v5: Unify spacing across components

[mdo]

• Updates horizontal padding across alerts, cards, dropdowns, list groups, and modals to be our default $spacer of 1rem
• Reassigns some variables to improve ease of customization
• Restyles the breadcrumb a smidge to make the background lighter for improved contrast and a little less vertical padding

Fixes #25057 for v5.

[MartijnCuppens]

The spacer changes LGTM.

Restyles the breadcrumb a smidge to make the background lighter for improved contrast and a little less vertical padding

Should be in another PR, or at least in a separate commit. Contrast ratio still doesn't meet 4.5 (4.26), but it's an improvement.

[mdo]

Restyles the breadcrumb a smidge to make the background lighter for improved contrast and a little less vertical padding

Should be in another PR, or at least in a separate commit. Contrast ratio still doesn't meet 4.5 (4.26), but it's an improvement.

Sounds good, I can re-split this shortly. I recall requests for removing the background and padding entirely on the breadcrumb—that might satisfy the color contrast issue then. Thoughts?

[MartijnCuppens]

Sounds good, I can re-split this shortly. I recall requests for removing the background and padding entirely on the breadcrumb—that might satisfy the color contrast issue then. Thoughts?

I'm ok with that. tbh, I regularly need to remove the background and paddings. The background, padding and border radius can be achieved with utilities anyway

[ffoodd]

The versions dropdown's current item's background is a bit stuck in .5rem :)

And for breadcrumbs, I strongly agree with @MartijnCuppens (and will probably try to get off every light gray background as of #30548).

Apart from this, I love spacing consistency!

[MartijnCuppens]

The left padding added by the ol should be removed from the breadcrumbs.

I also realised there is no .75rem padding utility, so maybe we should keep the paddings configurable (0 by default) and null-ify the once that are removed now.

Also the the breadcrumb looks so "naked" now: https://deploy-preview-30564--twbs-bootstrap.netlify.com/docs/4.3/components/breadcrumb/

[MartijnCuppens]

Maybe we should cover the breadcrumb changes in another PR, @mdo?

[mdo]

Removed breadcrumb restyling, updated the commits, and fixed the docs versions dropdown. Ready for review again!

[MartijnCuppens]

LGTM. Wonderful improvement, @mdo!

[ffoodd]

The only thing to question is having both $spacer / 2 and $spacer * .5: we may normalize this :)

[MartijnCuppens]

@ffoodd, good call, fixed that in the latest rebase