screenshot: Show a special error when screencast ran out of disk space

Since we now propagate error types back to gnome-shell now, let's start
with showing a special error message in case the disk ran out of space,
which is probably the most typical error.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2976>

js/misc/dbusErrors.js

@@ -51,6 +51,7 @@ export const ScreencastError = {
     ALREADY_RECORDING: 3,
     RECORDER_ERROR: 4,
     SERVICE_CRASH: 5,
+    OUT_OF_DISK_SPACE: 6,
 };
 export const ScreencastErrors =
     registerErrorDomain('Screencast', ScreencastError);