Mergeable lean testing PRs bot

Stream: batteries

[Kim Morrison]

Would anyone be willing to port the "Mergeable lean testing PRs" bot from Mathlib to Batteries? It would regularly, e.g. this evening, be useful in keeping Batteries up to date with nightly releases.

[Kim Morrison]

ah, I did it: https://github.com/leanprover-community/batteries/pull/1239