[dev] size-limit bot problems

[lobsterkatie]

[Note: These problems aren't unique to our repo, but they affect it, so it might make sense for either our team or @kamilogorek to tackle this. Also, https://github.com/getsentry/size-limit-action doesn't let you create issues.]

Two problems with the size-limit bot:

1. The comparison can be misleading, because AFAICT it always compares to master's HEAD commit, not the branch's base commit.

2. The skip_step config option never worked in the original size-limit action, and it similarly doesn't work for our fork. It's hard to figure out why - the code is very straightforward (see here) - but for some reason even though we've told it to skip the build step(here), it never does sometimes doesn't.

[kamilogorek]

Hmm I dont see it running a build? https://github.com/getsentry/sentry-javascript/runs/5675516647?check_suite_focus=true

[lobsterkatie]

Here is a recent run where it built before running the size check: https://github.com/getsentry/sentry-javascript/runs/5667939061?check_suite_focus=true

In that run, it finds the build cache, but then it isn't used.

(I updated the issue description to reflect that fact that it does sometimes behave as it should.)