This change introduces two new top-level options to the editor: `enableContentCheck` & `onContentError` for dealing with content supplied that does not match the prose-mirror schema generated by the set of tiptap extensions.
`enableContentCheck` allows the app developer to opt into the behavior to check for invalid schemas (this change is otherwise backwards compatible).
When true, this will try to parse the document, and any content that does not match the schema will emit a `contentError` which can be listened to via the `onContentError` callback.
