[libadwaita] (5 commits) Non-fast-forward update to branch wip/exalm/gi-docgen

[Alexander Mikhaylenko <alexm src gnome org>]

The branch 'wip/exalm/gi-docgen' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  abe35c8... Add gi-docgen subproject
  ebbeec7... Move docs to gi-docgen
  86a293b... ci: Drop an unused script
  0405b82... fixup

Commits added to the branch:

  c1e4dad... stylesheet: Special case colors for all flat buttons in hea (*)
  d5d2851... view-switcher: Use .flat buttons (*)
  bbeabc2... ci: Drop an unused script
  6da292e... Add gi-docgen subproject
  ff35e3c... Move docs to gi-docgen

(*) This commit already existed in another branch; no separate mail sent