Add a format value (MD or plain text) to charter and IESG ballot

[evyncke]

Description

Add a "format" choice (at least plain text -- default, or Markdown, or HTML) when creating/editing a charter or a ballot (possibly also BoF request, session agenda, ...) and of course use this format to render accordingly in the different views.

Code of Conduct

• I agree to follow the IETF's Code of Conduct

[evyncke]

Volunteering to make a limited implementation for the IESG ballots during the IETF-126 Code Sprint

[rjsparks]

The goal was that all charters are markdown (any that were entered as text would be rendered with markdown). You may remember an effort where we had chairs review the existing charters rendered this way. (I'll find the archive link later).

I strongly suggest ballots behave the same.

Accepting arbitrary HTML is problematic - why is markdown insufficient?

[evyncke]

HTML was added as an afterthought, better indeed to leave it out.

Ballots could be implicitily in markdown, even easier I guess.