I updated the base URI and included a Draft-specific info box section

[Dule-martins]

$ids were changed to absolute URIs. A Draft-specific Info block that supports changing dialects in an embedded schema (using $schema with a different value than the parent schema) with an explanation of the difference between 2020-09 and 2020-12

What kind of change does this PR introduce? refactoring doc

Issue Number:

• Closes #647

Screenshots/videos:

If relevant, did you update the documentation?

Summary

Does this PR introduce a breaking change?