Version 2.1.0

• Added support for Python 3.12.
• Fixed erroneous highlighting behaviour for code, code_block and print_code_block
  functions when None value was used for syntax_highlight parameter.
• Arbitrary string value can be now passed to syntax_highlight parameter
  of code, code_block and print_code_block functions. This allows to use languages
  supported by Highlight.js library.
• Internals:
  • Replaced with setup.py with pyproject.toml and Poetry, moved source code
    under src directory.
  • Dependency on pkg_resources replaced with importlib for Python >= 3.9.
  • Ruff is now used for linting and formatting.
  • Added missing py.typed file.