* docs: simplify schema organization and add modularize schema advanced section
* docs: working around code snippets demonstating how to organize a large schema
* update headers to be h tags and capitalization
* docs: intro to each file in modularize schema and circular reference full type defs
* docs: schema modularization formatting
* docs: shorten wording around intros to code snippets
* Move modularization to organizaition
* docs: removed circular dependencies section from schema organization
While the `gql` tag is not currently _required_, it does make it easier to
implement additional, development-friendly functionality in the future.
For example, it could avoid the need to question whether a string literal is
actually using Schema Definition Language (SDL) and avoid the need to
look for context clues.
By implementing these suggestions now, we can avoid the need to ask
developers to refactor in the future.
