[libadwaita] (48 commits) ...window-title: Convert docs

[Adrien Plazas <aplazas src gnome org>]

Summary of changes:

  4e4893f... Add gi-docgen subproject (*)
  e76ca7d... Move docs to gi-docgen (*)
  672e95c... action-row: Convert docs (*)
  390546c... animation: Convert docs (*)
  62cba1e... application-window: Convert docs (*)
  8777e8c... avatar: Convert docs (*)
  2080be6... bin: Convert docs (*)
  842c6d8... carousel: Convert docs (*)
  9f78b36... carousel-indicator-dots: Convert docs (*)
  e9604cb... carousel-indicator-lines: Convert docs (*)
  9ab7464... clamp: Convert docs (*)
  88a6d46... clamp-layout: Rewrite docs (*)
  ec3d6e3... clamp-layout: Convert docs (*)
  2b31d22... clamp-scrollable: Convert docs (*)
  19cdb9a... combo-row: Convert docs (*)
  7d0f8b1... enum-list-model: Add docs (*)
  52e6107... enum-value-object: Convert docs (*)
  7103b9f... expander-row: Convert docs (*)
  78e9bfe... fading-label: Convert docs (*)
  c4522b3... flap: Convert docs (*)
  5047a09... gizmo: Remove a doc section (*)
  aa0c7c8... headerbar: Convert docs (*)
  2ec1bff... indicator-bin: Convert docs (*)
  f5415a6... leaflet: Add missing docs (*)
  386a402... leaflet: Convert docs (*)
  a90490e... main: Convert docs (*)
  2430945... navigation-direction: Convert docs (*)
  6860f45... preferences-group: Convert docs (*)
  8fb0f0a... preferences-group: Mark title and description as nullable (*)
  8fbf09b... preferences-page: Convert docs (*)
  cbbf1f3... preferences-row: Convert docs (*)
  eccff03... preferences-window: Convert docs (*)
  7854d8f... shadow-helper: Remove the doc section. (*)
  599f3ba... squeezer: Convert docs (*)
  eafac3c... status-page: Convert docs (*)
  bbf5f61... swipeable: Convert docs (*)
  d287615... swipe-tracker: Convert docs (*)
  286fa8a... tab-bar: Convert docs (*)
  7f7f5d6... tab-view: Convert docs (*)
  6137bf0... value-object: Convert docs (*)
  3644cf9... version: Drop the doc header (*)
  9b1de4e... view-switcher: Convert docs (*)
  c393f3c... view-switcher-bar: Convert docs (*)
  00d0dbd... view-switcher-button: Convert docs (*)
  28bf1ba... view-switcher-title: Convert docs (*)
  02c5dde... window: Convert docs (*)
  959392d... window-mixin: Drop the doc header (*)
  b391dad... window-title: Convert docs (*)

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