Turn down this repository

[domenic]

@jyasskin, @johannhof and I will be working through the issue tracker to ensure all open discussions are closed or moved to their appropriate communities.

[RByers]

This deletes some text (eg. the intervention design guidelines) that we've occasionally pointed folks to as part of helping them think through how to make breaking changes that balance user value and developer frustration. Are there other equivalent resources we should be pointing folks to instead? Or perhaps we should put that into eg. chromium process docs instead of standards repos?
/cc @chrishtr

[johannhof]

@RByers Yeah, that's a good point. I agree that the content that we're overwriting here could be useful as permanent guidelines somewhere else, ideally with some modifications that outline the updated process (i.e. no longer having this repo) and how to move from intervention idea to web standard. I think the public Chromium docs would be an appropriate place for this.

I'm going to add this step to our internal planning. In the meantime it might make sense to leave this PR here as a signal of intent for now.