feat: configure build tools

[saep]

Description of changes

Add a build_tools option. Fixes #51

The default is { 'stack', 'cabal' }. This tries to run tests with stack, if the project contains a stack.yaml and falls back to cabal, if it is a Haskell/cabal project. Since Stack supports multi package projects, this check should is sufficient. I've tested it manually on the hspec project.

If the option is set to just { 'cabal' }, then cabal is always used to run the tests (if the project is a Haskell project).

Since I haven't really done any lua before, I'm looking forward to any suggestions to improve the code.

Things done

• [x] Tested, as applicable:
  • [x] Added plenary specs
  • [x] Manually
• [x] Updated CHANGELOG.md (if applicable).
• [x] Fits CONTRIBUTING.md

[saep]

I've also moved the project and package root logic into select_build_tool. This may also fix #47 ?

[mrcjkb]

I've also moved the project and package root logic into select_build_tool. This may also fix #47 ?

The impure bit checks if the package directory exists on the filesystem. I can probably just remove that.

[mrcjkb]

@all-contributors please add @saep for doc

[allcontributors[bot]]

@mrcjkb

I've put up a pull request to add @saep! :tada: