shall we bring back _test.md(x) as styling test and demo?

[hypha]

We used to have _test.md as a test & reference for markdown styling and component usage, but it was removed at some point. It was useful for checking how things render and how to use components. I think we should bring back something like that, update and maintain it. It'd be easier for teams to refer to it.

[artcz]

Yes please!

[egeakman]

This is done! Woohoo 🥳