Meta: Adding triage meeting introductory documentation

[Kaleidea]

@past The triage meeting seems to be very useful for the coordination of efforts and it was a valuable insight into the WHATWG's workflow, thank you for the invite!

I think it would be helpful for newcomers to have a short summary of the technicalities of how they can participate in the meetings. I myself had to guess and ask around. Although the answers turned out to be fairly straightforward, I had no way to know that beforehand.

I would write that intro if you agree. I'm wondering what you'd like to include and where it should be published: on the wiki for ex.?

[annevk]

To be clear, the triage meeting isn't an official part of WHATWG's workflow, but it's something we're experimenting with. WHATWG's Working Mode is explained here: https://whatwg.org/working-mode.

Having said that, I do think it would be useful to have an explanation of the triage meeting. I suggest we add it to the bottom of the README of this repository for now.

[past]

I don't feel strongly either way and I don't have much to offer on what the content would look like beyond my usual blurb in the issues. Anne's suggestion sounds fine to me.