[ENH] Add warning block and puts warning in a collapsable detail element

[Remi-Gau]

• closes Put warnings in a jinja block #23

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• add a test that throws warnings
• add a jinja black for warnings
• put warnings into a detail element

[Remi-Gau]

Sending snapshots eventhough the workflow seems to upload testing artefacts for quick inspection.

[Remi-Gau]

I know the styling needs more work: let me know what you would prefer and I can try to make it work.

I have started adding more styling things in a the downstream template that I use, but I am not sure it makes sense to put them in this PR.

For my usecase it makes sense to sort warnings by category first and then by file where they occur but maybe other people will want something different.

So let me know what you think would be a good default for the package.

[christiansandberg]

I think you need to update the CSS to reflect the extra level so that the badge and text aligns correctly.

If you have other improvements that would also be welcome. There is not much thought behind how the warnings are displayed.

[Remi-Gau]

Made some adjustments that should be fine in most use case (I hope)