Here are the issues concerning the CSS part, we encountered with @julien-deramond.
The commits can be splited if needed or wanted or even be in another PR. I'm open to every comment that could help fix these issues.
Tackled by the PR:
!important with (https://github.com/twbs/bootstrap/pull/36406/commits/ca48cc8d18b07fd011bab5052e726dced8446b35)
This PR adds a check for important utilities. It doesn't change anything on Bootstrap side, but might be useful for people that don't want !important in their code. If this commit is approved, it might lead to refactor some helpers' scss files.
Border-*-0 with (https://github.com/twbs/bootstrap/pull/36406/commits/adc78d0c843b005c49eb2cf975d468f9f8af2cf9)
This PR tries to make the .border-*-0 utility more understandable. It could be useful too, since the Stackblitz example doesn't take into account the examples' classes.
Rounded numbers with (https://github.com/twbs/bootstrap/pull/36406/commits/dee2d265d9a706d86105db2e8b14c7374e816268)
Having a rounded number of pixels for people that use 1rem = 16px.