ui: add label for every alert for different platforms

Author: Snyssfx

ui/src/pages/MainPage.vue

@@ -11,9 +11,9 @@ const app = useApp();
 
     <PlTextField v-model="app.model.args.name" label="Enter your name" clearable />
 
-    <PlAlert type="success" v-if="app.model.outputs.tengoMessage"> {{ app.model.outputs.tengoMessage }} </PlAlert>
+    <PlAlert type="success" label="Tengo message:" v-if="app.model.outputs.tengoMessage"> {{ app.model.outputs.tengoMessage }} </PlAlert>
 
-    <PlAlert type="success" v-if="app.model.outputs.pythonMessage"> {{ app.model.outputs.pythonMessage }} </PlAlert>
+    <PlAlert type="success" label="Python message:" v-if="app.model.outputs.pythonMessage"> {{ app.model.outputs.pythonMessage }} </PlAlert>
 
   </PlBlockPage>
 </template>