Add links to new features policy from other relevant places in the docs.

[finnlewis]

[aaronhirtenstein]

I think it would be useful to add links / reference on https://docs.localgovdrupal.org/devs/ in Quick Links and/or Get involved.

And maybe https://docs.localgovdrupal.org/devs/quality-standards/ since this is mostly aimed at people developing new features IMO.