Expose debugging information as global variables

[juliushaertl]

This came up during the contributor week that it would be great to expose certain state of the text app as global variables in OCA.Text so we can inspect the yjs, document and sync state in case of issues.

@max-nextcloud Could you look into this so ideally we have something for the next release and can investigate further for the issues that are still there?

[juliushaertl]

I'd imagine we have some OCA.Text.getDebugOutput() to export as much as possible so we can just ask people with issues to run this one thing.