Controller - Build has completed callback

[adrian-moisa]

We need a callback for detecting when the document plain text has changed but timed to be triggered after the build. Such that we can extract the latest rectangles as well. the current callbacks don't work:

• onReplaceText() - Called way to early, even before the document.changes stream
• document.changes - The stream emits only changes (not complete docs) before the build is completed
• onBuildComplete() - This one emits way too often, on hovering highlights, on selection changes, etc

Add new callback: onTextReplaceComplete(). Thanks to this new callback we can avoid comparing via onBuildComplete() the new text and the old text to see if the text has changed. Therefore the editor will be more performant, especially for large documents.