Fix #257

Author: lassekongo83

gtk/src/adw-gtk3-dark/gtk-3.0/meson.build

@@ -9,3 +9,6 @@ install_subdir('../../adw-gtk3/gtk-3.0/assets', install_dir : gtk3_dark_dir, str
 # In the gtk3 directory so we don't have duplicate the assets.
 install_data(['../../adw-gtk3/gtk-3.0/libadwaita.css'], install_dir: gtk3_dark_dir)
 install_data(['../../adw-gtk3/gtk-3.0/libadwaita-tweaks.css'], install_dir: gtk3_dark_dir)
+
+# Thumbnail for Cinnamon
+install_data(['thumbnail.png'], install_dir: gtk3_dark_dir)

gtk/src/adw-gtk3-dark/gtk-3.0/thumbnail.png

@@ -52,3 +52,6 @@ endforeach
 # In the gtk3 directory so we don't have duplicate the assets.
 install_data(['libadwaita.css'], install_dir: gtk3_dir)
 install_data(['libadwaita-tweaks.css'], install_dir: gtk3_dir)
+
+# Thumbnail for Cinnamon
+install_data(['thumbnail.png'], install_dir: gtk3_dir)