[#135] CI: add stylish-haskell and shellcheck

[Sereja313]

Description

Problem: We should add stylish-haskell and shellcheck to our pipline.

Solution: Add stylish-haskell and shellcheck. Use stylish-haskell on repo.

Related issue(s)

Fixes #135

✅ Checklist for your Pull Request

Ideally a PR has all of the checkmarks set.

If something in this list is irrelevant to your PR, you should still set this
checkmark indicating that you are sure it is dealt with (be that by irrelevance).

Related changes (conditional)

• Tests

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from
    silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • README
    • Haddock

• Public contracts

  • Any modifications of public contracts comply with the Evolution
    of Public Contracts policy.
  • I added an entry to the changelog if my changes are visible to the users
    and
  • provided a migration guide for breaking changes if possible

Stylistic guide (mandatory)

• My commits comply with the policy used in Serokell.
• My code complies with the style guide.

[dcastro]

I changed the base branch for this PR from master to Sereja313/#134-add-makefile.

Approved, but let's not merge this yet