Add dark theme for Web UI

webui/src/App.vue

@@ -15,6 +15,13 @@ export default {
 
     // debug
     console.log('Quasar -> ', this.$q.version)
+
+    this.$q.dark.set(localStorage.getItem('traefik-dark') === 'true')
+  },
+  watch: {
+    '$q.dark.isActive' (val) {
+      localStorage.setItem('traefik-dark', val)
+    }
   }
 }
 </script>