test(grimblast): take advantage of $BATS_TEST_DIRNAME. Fixes #182

[LeonardoMor]

Description of changes

Improve grimblast test setup by using the $BATS_TEST_DIRNAME variable provided by bats. Reference

Things done

• For new programs

  • Add the program to the README table, with yourself as the maintainer
  • Add a README for the program itself
  • Add Makefile (and Nix derivation optionally, otherwise @fufexan will do it)
  • If the program is a script, add it to the CI checks matrix

• For changes

  • Add changes to the CHANGELOG
  • Reflect your changes in the man pages (if they exist)

[fufexan]

Cool, LGTM.