fix: relative paths that work for GitHub readers

[jessicaschilling]

This PR fixes relative paths for GitHub-based readers. See ipfs/ipfs-docs#812 (comment) for more details.

[filecorgi]

• Image optimization came back clean!
• Vuepress build was successful!

docs/concepts/non-fungible-tokens.md:

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “its”.

  ...such a thing as "a single Bitcoin" with its own identity. Whereas cash at le...
                                             ^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “their”.

  ...ation model allows developers to create their own tokens, which can have spe...
                                             ^^^^^^^^^
  

• Possibly missing comma found.

  ...ken. # What makes a token non-fungible? Earlier we mentioned serial numbers ...
                                             ^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “its”.

  ...etwork alive, a blockchain incentivizes its own survival. As long as there a...
                                             ^^^^^^^
  

• Possibly missing comma found.

  ...of all historical data, including NFTs. IMPORTANT As we'll see in our discus...
                                             ^^^^^^^^^
  

• Possibly missing comma found.

  ...'s storefront or marketplace. # Looking ahead We are still in the early days...
                                             ^^^^^
  

• Possibly missing comma found.

  ...e will bring, but if you're here at NFT School you have a better chance than...
                                             ^^^^^^
  

docs/reference/metadata-schemas.md:

• The following link returned HTTP status code 301 (Moved Permanently):
  https://wikipedia.org/wiki/Metadata
• The following link returned HTTP status code 301 (Moved Permanently):
  https://ethereum.org
• The following link returned HTTP status code 302 (Found):
  https://binance.org
• If a new sentence starts here, add a space and start with an uppercase letter.

  ...ns new window). TIP If you're using nft.storage  (opens new window) to store...
                                             ^^^^^^^
  

docs/tutorial/end-to-end-experience.md:

• The following link returned HTTP status code 301 (Moved Permanently):
  https://docs.ethers.io/
• The following link returned HTTP status code 403 (Forbidden):
  https://cointelegraph.com/news/opensea-collector-pulls-the-rug-on-nfts-to-highlight-arbitrary-value
• The following link returned HTTP status code 302 (Found):
  https://nodejs.org
• The following link returned HTTP status code 308 (Permanent Redirect):
  https://nft.storage/login
• If a new sentence starts here, add a space and start with an uppercase letter.

  ...oring it on IPFS and Filecoin using nft.storage  (opens new window), all in ...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...an Ethereum testnet. # Why IPFS and nft.storage? Our example uses a free ser...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ... example uses a free service called nft.storage  (opens new window) to add a...
                                             ^^^^^^^
  

• Consider using an alternative to avoid wordiness and to strengthen your wording.

  ...istory. This provides accountability by making it clear to everyone what was...
                                             ^^^^^^^^^^^^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...s changed, when, and by whom. Using nft.storage, we can make our NFT data av...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...tomatically taken care of! Notably, nft.storage includes both long-term "col...
                                             ^^^^^^^
  

• Probable usage error. Use “and” after ‘both’.

  ...d Filecoin  (opens new window) network, as well as "hot storage" using IPFS ...
                                             ^^^^^^^^^^
  

• Possibly missing comma found.

  ...ou upload data to IPFS and generate NFT metadata all in one line of code. # ...
                                             ^^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...ens new window). Get an API key for nft.storage To make requests to nft.stor...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...for nft.storage To make requests to nft.storage, you need an API key. Login ...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...l upload your image and metadata to nft.storage  (opens new window), which w...
                                             ^^^^^^^
  

• The phrase ‘feel free to’ is used quite frequently. Consider using a less frequent alternative to set your writing apart from others and make it sound more professional.

  ...et into the details of the UI code, but feel free to tinker with it if you w...
                                             ^^^^^^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ... image and metadata onto IPFS using nft.storage  (opens new window). Then we...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ... function. # Uploading to IPFS with nft.storage Getting our data into IPFS i...
                                             ^^^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ... into IPFS is simple, thanks to the nft.storage client library  (opens new w...
                                             ^^^^^^^
  

• Use “an” instead of ‘a’ if the following word starts with a vowel sound, e.g. ‘an article’, ‘an hour’.

  ...object returned by the store method has a url property with the IPFS URI for...
                                             ^
  

• Possibly missing comma found.

  ... which is a helper provided by scaffold-eth to create a nice UI popup with t...
                                             ^^^