The three icons here are for Window Nativizer. They are fill-only paths on the
GNOME symbolic grid (16x16 viewBox, currentColor), which is what GTK recolors
to the row's own foreground; see AXIS_ICONS in src/prefs.js.

- winnativizer-corners-symbolic.svg: one rounded window corner. Drawn for this
  project, GPL-2.0-or-later like the rest of the repository.
- winnativizer-shadow-symbolic.svg: one window corner with a ring of dots
  along its outside, the shadow it casts. Drawn for this project,
  GPL-2.0-or-later.
- winnativizer-resize-symbolic.svg: the window resize cursor, a right-angle
  corner with an arrow to the top-left. Path taken from the Adwaita scalable
  nw-resize cursor shipped with gnome-shell (data/cursor-theme), MIT licensed,
  author Jakub Steiner; recolored and scaled to the symbolic grid. MIT is
  compatible with this project's GPL-2.0-or-later.

Registered on a bare icon-theme search path and named *-symbolic, so GTK treats
them as symbolic without an index.theme.
