GH action: Redeploy challenge on autograder

[carletex]

When we have austintgriffith/speedrun-grader#26, we can create a GitHub action (as in #350) to request a redeploy for a given challenge to the autograder.

Maybe only when test changes? I guess that'll be enough, since we don't care if the contract changes..... if the test remains the same, right? But maybe we can do it with both.

[carletex]

austintgriffith/speedrun-grader#27 Merged!

I sent you the API key on DM