It's not clear what's worthy of relnotes

[workingjubilee]

Not everything that should go in relnotes is flagged with the relnotes label. This is partly because it's not clear what is worth flagging with relnotes. I certainly have spent almost zero time thinking about whether I should be tagging things with relnotes, regardless of how impactful a change might be.

The dev guide mentions the relnotes label and what it means but doesn't explain how to decide when to assign it.

[jieyouxu]

This is also unclear in the reviewer guidance in the forge docs.