Feat/support editor by mime type

[easylogic]

Do not merge this PR.

What this PR does / why we need it?

You can edit other documents based on their type.

Any background context you want to provide?

• Specify the mimeType when initializing the document.
• Render a different editor based on the mimeType.
• support editor
  • markdown - text/markdown (default)
  • whiteboard - application/whiteboard (not yet)
  • cell - application/cell - (not yet)

What are the relevant tickets?

Fixes #

Checklist

• [ ] Added relevant tests or not required
• [ ] Didn't break anything

[hackerwins]

Continue with #250