Add .cabal and cabal.project as recognised file types for comments

[ozkutuk]

This PR adds .cabal and cabal.project as recognized file types for comments. These files are used by the Cabal build tool.

• Added a change log entry in changelog.d/<directory>/.
• My changes do not contradict
  the current specification.
• I agree to license my contribution under the licenses indicated in the
  changed files.

[ozkutuk]

Hmm, I have now realized that the modified .cabal files are not accepted by Cabal anymore, because Cabal mandates that the cabal-version field is the first thing that appears in the file, apparently including comments:

Errors encountered when parsing cabal file ./test.cabal:

test.cabal:6:1: error:
cabal-version should be at the beginning of the file starting with spec version 2.2.
Current cabal-version values are listed at https://cabal.readthedocs.io/en/stable/file-format-changelog.html.

    6 | cabal-version:      3.0
      | ^

There is nothing wrong with this PR per se, but this will probably not be of much use unless this is somehow resolved on the Cabal side.

[carmenbianca]

LGTM, thank you @ozkutuk

[carmenbianca]

Oops, I hadn't read your second comment! That is indeed a bit of a thing. You could solve that by adding cabal-version: as a shebang to the HaskellCommentStyle class. It's not 100% perfect, but should work.