Jinja support - rebased

[thibaudcolas]

See #247 – rebased, with additional tests and documentation

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have added an appropriate CHANGELOG entry

[Copilot]

Copilot reviewed 40 out of 46 changed files in this pull request and generated 1 comment.

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• tests/jinja/non-patterns/include.html: Language not supported
• tests/jinja/non-patterns/variable_include.html: Language not supported
• tests/jinja/patterns_jinja/base_jinja.html: Language not supported
• tests/jinja/patterns_jinja/base_page_jinja.html: Language not supported
• tests/jinja/patterns_jinja/components/accordion/accordion.html: Language not supported
• tests/jinja/patterns_jinja/components/button/button.html: Language not supported