ci: include rustfmt and clippy PR checks

[calebcartwright]

Changes

• Adds rustfmt PR check
• Adds clippy PR check (fails on warnings, runs against all targets)
• Fixes clippy findings

Related Issues

• Closes Add PR builds for rustfmt and clippy #57

[codecov]

Codecov Report

Merging #71 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #71   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           4      4           
  Lines         169    169           
=====================================
  Hits          169    169

Impacted Files	Coverage Δ
src/hooks.rs	100% <ø> (ø)	⬆️

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[calebcartwright]

The coverage thing is really weird. I had the explicit return statements in that file even though it's unnecessary/not the idiomatic way, because I'd seen this before where kcov seems to think the closing } of the function is uncovered... somehow

🤷‍♂

I've reverted back to the explicit returns with a clippy disable