export-zips: Pick up non-default stylesheets

The window-list extension is about to import the workspace-indicator
stylesheet. Explicitly pack css files, so the stylesheet is included
in the bundle.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/307>

export-zips.sh

@@ -39,7 +39,7 @@ for f in $extensiondir/*; do
   fi
 
   cp $srcdir/NEWS $srcdir/COPYING $f
-  sources=(NEWS COPYING $(cd $f; ls *.js))
+  sources=(NEWS COPYING $(cd $f; ls *.js *.css 2>/dev/null))
 
   [ -d $f/icons ] && sources+=(icons)