Docs: horizontal scroll on small screen/mobile

[patrickhlauke]

There are 5 instances in our current documentation where, on a mobile device, there's an unsightly horizontal scroll due to elements being wider than 100% of the viewport.

Although these appear in the documentation, some of them may point to things that need fixing in core bootstrap regarding width/margins/responsiveness.

The below were found testing the docs as they stand just now in repo, using Chrome DevTools device emulation set to iPhone 6 (375px width)

Components > Buttons

Components > Input groups

Components > Modal (addressed by #24878)

Components > Pagination

Utilities > Text

[patrickhlauke]

To purely address the "don't make docs scroll horizontally" issue, added all necessary fixes to #24878

However, the root issue of why button groups, custom file inputs and large pagination cause an overflow in the first place / don't adapt to the correct width should likely still be investigated properly.