Plugins: adds languages to the plugin schema (#109949)

docs/sources/developers/plugins/plugin.schema.json

@@ -685,6 +685,13 @@
           }
         }
       }
+    },
+    "languages": {
+      "type": "array",
+      "description": "The list of languages supported by the plugin. Each entry should be a locale identifier in the format `language-COUNTRY` (e.g., `en-US`, `fr-FR`, `es-ES`).",
+      "items": {
+        "type": "string"
+      }
     }
   }
 }