Rollup merge of #22282 - steveklabnik:gh5831, r=brson

This redux of CONTRIBUTING.md adds in more information, including
subsuming both compliment-bugreport.md and Note-development-policy
in the wiki.

I only glanced at the broad TOC of Note-development-policy, and did
not use the text as the basis for the re-write. This will then address
the last outstanding part of #5831.