docs: Add dynamic plugin setup/installation instruction for the janus…

…-idp plugins (#1195)

* RHIDP-1127: Add dynamic plugin setup/installation instruction for the janus-idp plugins

* Using app-config.local.yaml

README.md

@@ -12,6 +12,50 @@ A subset of available Janus IDP plugins is available at our [community site](htt
 
 You can also see the [Plugin Marketplace](https://backstage.io/plugins) for other open-source plugins you can add to your Backstage instance.
 
+## Dynamic Plugins Installation
+
+It is possible to install plugins without code changes in a backstage that supports [Dynamic Plugins](https://github.com/janus-idp/backstage-showcase/blob/main/showcase-docs/dynamic-plugins.md) (e.g. [Janus IDP](https://janus-idp.io/) and [Red Hat Developer Hub](https://developers.redhat.com/rhdh)). Follow the steps below to install a dynamic plugin:
+
+- Map the dynamic plugins root directory in `app-config.local.yaml`:
+
+```
+dynamicPlugins:
+  rootDirectory: dynamic-plugins-root
+```
+
+- Place your package inside the plugins root directly. You can pack a local plugin or download from NPM using `npm pack`, then make sure to extract it correctly into the plugin root directory:
+
+```
+cd dynamic-plugins-root
+mkdir {plugin name}
+tar -xzvf {path to the NPM package tgz file} -C {plugin name}  --strip-components=1
+```
+
+- Configure your plugin in `app-config.local.yaml`. For example, the configuration below will make a new menu item to access the plugin on route `my-plugin`:
+
+```
+dynamicPlugins:
+  rootDirectory: dynamic-plugins-root
+  frontend:
+    {plugin name}:   # this should match the plugin name in package.json, remember to remove "@" and replace "/" by dots (".")
+      pluginConfig:
+      dynamicRoutes:
+        - path: /my-plugin
+          importName: MyPlugin   # the exported react component that should be rendered
+          menuItem:
+            text: My Plugin
+```
+
+- Start backstage and you should see in logs that your plugin was correctly scanned by Backstage:
+
+```
+scalprum info Loaded dynamic frontend plugin '{plugin name}' from '${Backstage path}/dynamic-plugins-root/{plugin name}'  type=plugin
+```
+
+Now when accessing Backstage you should see a new menu item with name `My Plugin` and when clicking on it your plugin will be rendered.
+
+For more information check the [Dynamic Plugins Guide](https://github.com/janus-idp/backstage-showcase/blob/main/showcase-docs/dynamic-plugins.md).
+
 ---
 
 ✨ We would love for you to contribute to Janus IDP's collection of Backstage plugins and help make it even better than it is today! ✨