Add linting/formatting with djlint

[krukas]

Use https://github.com/djlint/djLint to add support for linting and formatting:

Formatting example: https://pygls.readthedocs.io/en/latest/examples/formatting.html Linting (diagnostics) examples:

• https://pygls.readthedocs.io/en/latest/examples/publish-diagnostics.html
• https://pygls.readthedocs.io/en/latest/examples/pull-diagnostics.html