Fix ligatures

[brunobord]

closes #2

Checklist

• [x] Adding unittests.
• [x] Editing the input.html and expected.html files to add examples in the "Les exemples" and the "Et si le texte est déjà correct…" sections.
• [x] Add the fix_<feature> flag
  • [x] Cover the True/False cases,
  • [x] Add the param help text in the function docstring,
  • [x] Add the skip_feature argument for the CLI tool,
  • [x] Test the parameters,
• [x] Changelog entry.