add dconf sandbox permissions, needed for file chooser dialogue

org.gnome.Organizer.json

@@ -14,7 +14,11 @@
         "--filesystem=xdg-download",
         "--filesystem=xdg-music",
         "--filesystem=xdg-pictures",
-        "--filesystem=xdg-videos"
+        "--filesystem=xdg-videos",
+        "--filesystem=xdg-run/dconf",
+        "--filesystem=~/.config/dconf:ro",
+        "--talk-name=ca.desrt.dconf",
+        "--env=DCONF_USER_CONFIG_DIR=.config/dconf"
     ],
     "build-options" : {
         "cflags" : "-O2 -g",