Add callouts about using light colors ideally on a dark background

[patrickhlauke]

would be even better to show those buttons on a dark background, but i assume that'd require a lot more logic behind the scenes (to only show the outline buttons that are contrasty enough against white on a white background, and the others on a dark background)

[ffoodd]

With #30044 merged a few days ago, it might be quite trivial to handle backgrounds (but would require to use some kind of containers to apply backgrounds). However the callout is a good idea :)

[patrickhlauke]

Just realised we should probably do the same for https://v5.getbootstrap.com/docs/5.0/helpers/colored-links/ ... i'll add another commit here

[mdo]

Would be very nice to add a background element around them if needed based on the contrast colors. A callout like this feels unnecessary IMO, but I'm down for whatever.

[patrickhlauke]

let's do callout just now, and then somebody cleverer than me can work out how to do a conditional bit of light vs dark background

[XhmikosR]

@patrickhlauke this needs a manual backport, can you do it please and ping me?

[patrickhlauke]

@XhmikosR done - #32054