* v4-dev: (56 commits)
  Remove unnecessary brackets for consistency (twbs#27966)
  Fix Typo on docs (twbs#27962)
  Add a few more redirects.
  Remove wrapping paragraph in readme (twbs#27948)
  Configurable display utility classes (twbs#27917)
  Fix custom select font sizes (twbs#27929)
  Match input font size for `.input-group-text` (twbs#27941)
  reboot: Fix comment (twbs#27937)
  Fix form-feedback-icon-invalid color (twbs#27935)
  toasts: mention that positioning is manual. (twbs#27931)
  stretched-link.md: fix typo (twbs#27918)
  Add Open Collective to header (twbs#27916)
  Add horizontal card example (twbs#27906)
  getSelectorFromElement return null on bad selectors (twbs#27912)
  versions: sort from newer to older. (twbs#27898)
  Fix 4:3 embed (twbs#27910)
  Simplify card group css (twbs#27901)
  Blacklist border-radius property (use mixin instead) (twbs#27900)
  move to 4.2
  bootstrap-stack.svg: remove unneeded space.
  ...