[gnome-games] (19 commits) ...preferences-page-video: Wrap into a HdyColumn

[Alexander Mikhaylenko <alexm src gnome org>]

Summary of changes:

  c8b0016... flatpak: Build libhandy (*)
  7d6237b... ci: Build libhandy for cross_distro targets (*)
  3f94eb5... build: Add libhandy dependency (*)
  929fb28... ui: Add css from libhandy example (*)
  cf5eba7... preferences-window: Add .sidebar style class to separators (*)
  394c555... preferences-window: Wrap titlebar into a HdyTitleBar (*)
  9a1ec7e... ui: Add PreferencesSubpage (*)
  5e93e78... preferences-page: Add 'subpage' property (*)
  7b59e7e... preferences-window: Integrate subpages (*)
  31b1c39... preferences-page-controllers: Rename on_back() to on_back_c (*)
  4d1bfc1... ui: Convert GamepadConfigurer into a subpage (*)
  7253efc... ui: Convert KeyboardConfigurer into a subpage (*)
  d607ad2... preferences-page-controllers: Simplify layout (*)
  a0c0ea8... ui: Remove immersive mode from preferences (*)
  de25017... ui: Remove visible_page_changed() from PreferencesPage (*)
  4d8e42b... ui: Drop custom headerbars from preferences pages (*)
  461d4dd... preferences-page-controllers: Wrap into a HdyColumn (*)
  f759ebb... preferences-page-plugins: Wrap into a HdyColumn (*)
  ba43f0f... preferences-page-video: Wrap into a HdyColumn (*)

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