Fix disabled floating labels and add some examples of it in the docs

[julien-deramond]

Description

• Fixes the rendering when a disabled input is used in a floating label
• Add some documentation to reflect this use case

Motivation & Context

I'm suggesting to add a new "Disabled" section in the documentation to be consistent with other form controls, and it will help us detect regression in the future.

Type of changes

• Bug fix (non-breaking change which fixes an issue)

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-37299--twbs-bootstrap.netlify.app/docs/5.2/forms/floating-labels/#disabled

Related issues

Closes #37297
Closes #37330 (and might replace #37359)

[mdo]

I think this might not work for <textarea>s—can you double check and add a disabled example for that as well?

[julien-deramond]

The second example is already a disabled <textarea>. You mean maybe a disabled <textarea> with a custom height?

[mdo]

The second example is already a disabled <textarea>. You mean maybe a disabled <textarea> with a custom height?

Doh, my bad haha. Yes, please!

[julien-deramond]

Done via 17989d6. I've let both the normal <textarea> and the custom one, IDK if it is a good idea or not. Maybe the custom one is enough 🤷

[AgentSmith0]

Thanks!