(again)

https://github.com/twbs/bootlint/wiki/W007

Specify new height for inputs in floating label example after v4.1.3's addition of a fixed height property on .form-control

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* Flexbox based sticky footer

* Update guide message

* Use utility classes instead of custom CSS

Fixes #26281

- Splits the examples with code snippets
- Adds note about possible broken visuals

Closes #25813

closes #26586, closes #26587

see #22944 and #24620

With the current docs directory setup, I'm making too many mistakes and have to manually address path changes and directory moves on deploy. This makes for a frustrating experience developing locally and shipping releases. With this PR, we're basically back to the same setup from v3—duplicating the dist directory into our docs directory. Not the most ideal, but very straightforward for me as the release manager.