Add Rmarkdown files to parsable-R hook

[pwildenhain]

Closes #319

[lorenzwalthert]

Looks great overall, I adjusted the docs for the vignette on available hooks and pushed one cosmetic change (use tempfile() directly). Also, you added your test to test/testthat/test-all.R. This file was renamed to test-hooks.R and should not be around (but was recovered in some git operation). I'll delete it in a separate PR, but can you add your tests to tests/testthat/test-hooks.R instead? I you don't want or it's too complicated, I can do it.

[pwildenhain]

Also, you added your test to test/testthat/test-all.R.

It's funny, I originally did add this to test-hooks.R but when I went back and read the CONTRIBUTING.md I added it to test-all.R 😂

I'll make that change, and then make a few updates to CONTRIBUTING.md in a separate PR

[lorenzwalthert]

Also, all errors you see are unrelated.

[pwildenhain]

The CONTRIBUTING.md also mentions needing to add the hook script to the inst/bin directory -- is this still the case? I only made changes to inst/hooks

[lorenzwalthert]

That directory was renamed to inst/hooks/exported, so please use this path.

[lorenzwalthert]

Thanks again @pwildenhain 🥳