feat: render plugin download UI on event

Author: rdsov

packages/openscd/README.md

@@ -29,6 +29,7 @@ Once Node.js is installed on your system, you may get started by entering the fo
 git clone https://github.com/openscd/open-scd.git
 cd open-scd
 npm install
+npm run build
 npm start
 ```
 

packages/openscd/src/addons/Layout.ts

@@ -327,6 +327,10 @@ export class OscdLayout extends LitElement {
         this.requestUpdate();
       }
     );
+
+    document.addEventListener("open-plugin-download", () => {
+      this.pluginDownloadUI.show();
+    });
   }