Setup project

[dcastro]

We need the following:

• [ ] a buildkite pipeline
  • [x] reuse checks
  • [x] trailing-whitespace-check
  • [x] check cabal files match the stack files
  • [x] weeder
  • [x] run bats tests
  • [x] xrefcheck
  • [ ] run doctests
• [x] code_style.md document
• [x] CONTRIBUTING.md
• [x] makefiles
• [x] support for cabal & stack
• [x] tasty test suite
• [x] github issue/pull request templates
• [x] license files
• [x] stylish-haskell
• [x] hlint
• [x] .editorconfig

See templates here: https://github.com/serokell/metatemplates

Let's wait until #7 is merged before we add code-formatting tools (stylish-haskell and hlint)