ci: replace outdated Github action with Nix and Prettify

[drupol]

This PR:

• Replace the Github action with Nix Prettify command

[drupol]

@jtojnar WDYT about this?

[jtojnar]

I do not think prettier will check Nix files? Also the workflow should probably be renamed. And the formatting should be performed before checks so that there are no red commits.

[drupol]

I do not think prettier will check Nix files? Also the workflow should probably be renamed. And the formatting should be performed before checks so that there are no red commits.

Indeed, prettier does not check .nix files, this is why I'm introducing #190 as well.

I will rebase the commits to fit your request right now.

[shyim]

Can you not run configure nix fmt and then use that tool here and check that the git diff is empty?

[drupol]

prettier does not format .nix files, so, it would be useless to do that.

For nix files, I created this PR: #190