Update dependencies and drop Node.js < 20 support

[XhmikosR]

Needs some work mostly due to the order errors. Unsure how to make it work like before.

The deprecated rules are probably valid and something Bootstrap v6 could benefit, maybe minus the clip error?

/CC @julien-deramond in case you have any ideas.

PS. I had to disable color-function-alias-notation in scss files because it incorrectly changed things, I think. Feel free to revisit as needed and push to this branch.

PPS. There might be other rules we override that could change like dropping scss/no-global-function-names and selector-not-notation.

[julien-deramond]

Thanks for the ping! I have to admit I'm not deeply familiar with how this package's version is synced to Bootstrap's versions in practice for major versions, so I might be off here (and I won't be able to look into this properly for at least a week, sorry about that).

From what I understand though, would something like this make sense?

• Bootstrap 5 stays on Stylelint 16 (v16.x of this package). Since v5 will be more in maintenance mode once v6 alpha is out, I'm not sure it's worth taking on a major tooling bump, especially if it requires SCSS source changes. Whether we'll cut another v5 minor is also unclear for now.
• Bootstrap 6 would then adopt the new version coming out of this PR, since v6 is already heading toward Sass modernization (including the switch to Sass modules), which would possibly change the approach to things like scss/no-global-function-names, color-function-alias-notation, and the other rules you mentioned.

Does that even make sense as a strategy, or am I missing something? Would love your take before I properly test this config against v6-dev when I'm available.

@mdo you might have some input here too, as the person who has worked the most on the Sass side of v6-dev.