Self-hosted images

[bgmort]

This is a feature request: I'd like to be able to have the generator request and save the images so they can be hosted with the blog. Then I believe the whole site can be served without making any requests to notion's servers. This has a few benefits:

• Images aren't broken if notion changes the image urls
• The site can be viewed locally without an internet connection
• The source Notion table can be un-shared after generation, protecting potentially sensitive info such as unpublished drafts