preferences: render 'markdownDescription' as markdown

[vince-fugnitto]

Prerequisite:

Following #7105

Feature Description:

It is possible to define a markdownDescription property for preferences in the schema, which is ultimately used as a description of the preference including the tooltip (when editing JSON), and in the user-interface. In the user-interface, the markdownDescription should be properly rendered as markdown similarly to VS Code:

Theia:

VS Code:

[jwebstar]

I started on this while looking at the new preferences UI and have made some progress:

Before:

After:

But I haven't got the internal settings links working yet. Rather than scrolling to that preference, clicking a link currently appends the id to the url instead. Before resuming with it I wanted to check:

1. If anyone has any guidance on how this should be done?
2. That nobody was already working on this?

[vince-fugnitto]

@jwebstar sorry for getting back so late, it already looks like some great progress! 👍

1. If anyone has any guidance on how this should be done?

I haven't looked at it closely yet as what we could do but we can probably use the same idea we had in #9318 to give the links the role of buttons and attempt to scroll-to the proper preference. Still, please feel free to open a draft pull-request with the changes so far and perhaps others can help.

2. That nobody was already working on this?

Not that I know of :)