Allow the creation of Sites with Builder

[BobWez98]

This PR does a few things.

• Solves Allow Sites to be registered via the Statamic Builder. #25
• Drops the support for Statamic 4, because it's using Statamic 5 functionality in the registering of the sites
• Removes composer.lock so projects can figure out what versions match
• Ran pint

[tdwesten]

Hi @BobWez98,

Thank you for adding this! I tested it locally, and it works as expected. If you include the warning about clearing the cache, it will be ready to merge.

🙏

[BobWez98]

Hi @tdwesten, you're welcome! Where would you like to see the warning?

[tdwesten]

Hmm, near the "How to Create a Site" instructions :)

[BobWez98]

Like so?

[tdwesten]

Yeah super!