Disambiguate that "labels" refers to Github issue labels

[lostfictions]

Hi there, just spent a bit of time trying to get this to work with my project. Peeking at the issues, it looks like this has maybe been brought up before -- it's really not obvious that this sentence:

By default lerna-changelog will show all pull requests that have been merged since the latest tagged commit in the repository. That is however only true for pull requests with certain labels applied.

Refers specifically to Github issue labels -- I thought it meant "labelled" commit prefixes (for example, as defined by Conventional Commits). Maybe a slightly longer explanation would be helpful? Or even an image of Github issue labels to underline the point?

Incidentally, it's very confusing when the lerna-changelog command emits no output and gives no feedback. I think it'd be really great if it could be a little more verbose about errors for common failure modes (like this one described in this issue!).