Add djLint formatter/linter for Jinja templates

[akbarkz]

Done

• Added djLint fotmatter/linter support
• Defined a configuration file .djlintrc for it
• Added a yarn script lint-jinja that checks linting in Jinja templates that were changed
• Added GH CI job for running lint-jinja script

QA

• Set up djLint in your codebase as described in Discourse topic here: https://discourse.canonical.com/t/configuring-editors-for-formatting-and-linting/188
• Open any Jinja template and format it
• Save the formatted file
• Run yarn lint-jinja script in the terminal and check that it has checked one changed file and that the check has passed
• Change another Jinja template and save it without formatting it
• Run yarn lint-jinja and check that the file is reported as having a linting error
• Open the file and check where djLint is reporting errors by hovering on places that are highlighted red
• Format the file and fix remaining linting errors and save
• Run yarn lint-jinja again and check that the file has passed the linting check

Issue / Card

There is no issue

[webteam-app]

Demo starting at https://canonical-com-1224.demos.haus

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 66.14%. Comparing base (b9323f4) to head (2639e8a). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1224 +/- ## ======================================= Coverage 66.14% 66.14% ======================================= Files 10 10 Lines 898 898 ======================================= Hits 594 594 Misses 304 304 ``` | [Flag](https://app.codecov.io/gh/canonical/canonical.com/pull/1224/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical) | Coverage Δ | | |---|---|---| | [python](https://app.codecov.io/gh/canonical/canonical.com/pull/1224/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical) | `66.14% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=canonical#carryforward-flags-in-the-pull-request-comment) to find out more.

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