Add caching dupe change

[dorryspears]

This closes #340. I tried putting the yaml in the workflow folder for the new cache job but it wasn't able to find it, so I made it an action.

[joshlf]

Thanks for this, @dorryspears !

I'm not a GitHub Actions expert, so I may be off the mark here, but will making this a "step" rather than a needs dependency mean that this action is executed multiple times? Currently (on main), it executes once at the beginning of the job run and then the results are re-used by all steps, which helps things run faster.

[dorryspears]

@joshlf You are right. I now understand what the CI was doing. I rearranged my code and added back the generate cache step. That action just replaces the

- uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
      with:
        path: |
          ~/.cargo/
        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}

step in the existing jobs.

[joshlf]

Okay awesome, thanks! A few nits regarding stray whitespace, but this looks good!