chore: fix doc

chore: fix init plugin manifests stream

src/plugin/request.md

@@ -9,7 +9,7 @@ Be it request the user to select a region, a point, navigate to a specific locat
 ```javascript
 
 let parentWindow
-window.addEventListener('message', ev => {
+window.addEventListener('message', msg => {
   const { source, data, origin } = msg
   const { id, method, params, result, error } = data
 

src/plugin/service.ts

@@ -6,6 +6,7 @@ import { WidgetPortal } from "src/widget/widgetPortal/widgetPortal.component";
 import { setPluginSrc, SET_PLUGIN_NAME } from "./const";
 import { PluginPortal } from "./pluginPortal/pluginPortal.component";
 import { environment } from "src/environments/environment"
+import { startWith } from "rxjs/operators";
 
 @Injectable({
   providedIn: 'root'
@@ -25,7 +26,9 @@ export class PluginService {
     'siibra-explorer': true
     name: string
     iframeUrl: string
-  }[]>(`${environment.BACKEND_URL || ''}plugins/manifests`)
+  }[]>(`${environment.BACKEND_URL || ''}plugins/manifests`).pipe(
+    startWith([])
+  )
 
   async launchPlugin(htmlSrc: string){
     if (this.loadedPlugins.includes(htmlSrc)) return