feat: kroki.io integration

You can create diagrams-as-code instead of implementing mermaid, exaclibur, ....
Gitlab is doing well this feature.

We already have many diagram integrations as you know already.
I do understand that Kroki has support for many other diagram types, but we have no plans for it at this time.

Merge pull request 'feat(editor): тело страницы из локального ydoc, r…