add xxl size modal

[TommasoAllegretti]

Description

add xxl modifier for modal

Motivation & Context

as requested in issue #39433

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-39477--twbs-bootstrap.netlify.app/docs/5.3/components/modal/#optional-sizes

Related issues

Closes #39433

[coliff]

Thanks for making this PR based on the issue I opened. :-)

If it's approved we'd need to update the Modal docs too:
https://github.com/twbs/bootstrap/blob/v5.3.2/site/content/docs/5.3/components/modal.md#optional-sizes

[TommasoAllegretti]

In case this PR gets approved I went ahead and added the necessary documentation.
Feedback is very welcome as this is my first contribution.

[julien-deramond]

Thanks for creating this PR @TommasoAllegretti

Apart from the possible issue in scss/_modal.scss, the code looks good to me!

However, we still to determine if we want this modal variant to be added to our build.
I'll let @twbs/css-review add their thoughts, but on my side, I wouldn't mind adding it since the CSS bundle wouldn't grow too much, and it seems consistent with what we provide for fullscreen modals, XXL containers, etc.

While we are deciding, I'm going to add the corresponding issue to the v5.4 project and set its state to "Review in Progress". Indeed, being a new feature, it couldn't be added before in a v5.3.x.

[julien-deramond]

The techinal part LGTM! Let's wait for the feedback of the rest of the team to see if this new feature can be embedded (in v5.4 or after) or not.

[louismaximepiton]

I feel fine with the technical part as well and it feels right to have this kind of variant, we have those almost everywhere in the doc.

The only drawback I can see is kind of not related to this PR:
Should the lg, xl and xxl modals be "fluid" until they reach their maximum width ? The following image feels wrong to me. It could be done afterwards anyway.

[mdo]

Works for me, as does @louismaximepiton's suggestion I think.