Performance test suite

I'm currently using https://github.com/Razzeee/tree-sitter-elm/blob/master/script/parse-examples-full to parse all of the packages on the elm package website and some hand picked open source applications.

I think it would be nice to have this for elm-format too. I would try to print the timings for each, so that we can see how changes to elm-format impact these and we can reference back to changes as log as the CI logs are still around.

I'm currently using github actions https://github.com/Razzeee/tree-sitter-elm/commit/c8fd1b94446bfaada9b3f39b3b60fcfe2374dbb0/checks?check_suite_id=303385075 which I would recommend as we can run the script on linux and macos then (travis would also work, but feels slower and would be more work for me) , unfortunatly due to it being a bash script windows is not possible.

Let me know what you think and I will start working on it.

Start by reviewing the referenced script/parse-examples-full and the linked GitHub Actions run to understand the proposed corpus and CI setup. Define the elm-format performance suite around parsing the Elm package and application examples, with timings for each input and Linux/macOS CI results that can be compared over time.

Written by the indexing model from the issue text.