Add info about static files (#19965)

packages/grafana-toolkit/README.md

@@ -213,6 +213,9 @@ module.exports = {
 };
 ```
 
+### How do I add 3rd party dependencies that are not npm packages?
+You can add such dependencies by putting them in `static` directory in the root of your project. The `static` directory will be copied when building the plugin.
+
 ## Contribute to grafana-toolkit
 You can contribute to grafana-toolkit in the by helping develop it or by debugging it.