Support $app in type name

The `$app:` prefix turns into a namespace using the Shopify app's idea. The diff logic in this library doesn't account for it and tries to recreate the metaobject definition.

For now I'll probably manage my own GraphQL queries, but I'd like to revisit updating this library after!

Start by locating the library's diff logic that handles type names and compare its behavior for the `$app:` prefix. Confirm how Shopify app namespaces are represented, then verify that a `$app:` type name is recognized without attempting to recreate its metaobject definition; the issue mentions managing GraphQL queries as a current workaround.

Written by the indexing model from the issue text.