As discussed some time ago on the dev call, we need better GitHub labels to manage issues and PRs.

I don't think we'll manage to rebuild labels from scratch (or if we do, that it would be the perfect system). Therefore I propose to incrementally evolve the labels.

I've collected all present labels in a google spreadsheet

I did a rough classification:

• State: Something to do with "next action"
• Topic: Which part of matplotlib does it address?
• Scope: This is only sort of a collection of non-state non-topic labels. One might split or rename this, but it's currently not my focus.

For now, I'm focussing on State, because the notion of "next action" has been identified to be important (c.f. https://hackmd.io/P3Hrfoy9RSKRA4-mXMKW2A#PR-closing-philosophy).

I propose the following:

• Rename all state labels label name to state: label name.
  Rationale: The prefix distinguishes these labels from other classes (which may or may not grow a prefix themselves later on).
• Change the colors to a simple 4-color scheme based on who must do the next action to move the issue/PR forward:
  
  Rationale: By this coloring we can immediately see whether the issue/PR needs an action from our side, which is the most important aspect for issue management. IMO the 4 colors are enough. One could add slight variations, e.g. different greys for different "no action" labels, but then again, nobody will exactly remember these. So let's keep it simple for a start. We can still refine this later if needed.