Include some workflow commands in Contributing.md

[santiweight]

Some that I have been using:

cabal-docspec --check-properties cabal v2-test --enable-coverage

Nothing too crazy. Might be good to add a "contributor's check" script?

This is very low priority.

[tonyday567]

I just used:

hlint . ormolu --mode check $(git ls-files '*.hs') cabal haddock --enable-documentation

[santiweight]

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