Regression Benchmarking

[j-mie6]

As we build more and more functionality into the library, it would be a good idea to make sure that we don't do anything that inadvertently cripples the efficiency. I propose the following:

1. Write a selection of benchmarks using tasty-bench as a test suite (these will also be able to serve as integration tests!)
2. If the commit is tagged write these results to a .csv file, and push them into a bench-data branch under tag.csv
3. On push, if there is a previous tag on this branch (or main) pull down the csv file for that tag, and use it as a comparison, allowing us to test that things don't deviate too much.

Some resources on this:

• https://hackage.haskell.org/package/tasty-bench -- in particular the "Comparison against baseline" section
• https://stackoverflow.com/questions/69577518/github-action-to-copy-specific-folders-from-one-branch-to-another-in-the-same-re