feat: added router.rendered promise

Author: jakobrosenberg

lib/runtime/Router/Router.js

@@ -108,6 +108,11 @@ export class Router {
         (!this.pendingRoute.get() && this.activeRoute.get()) ||
         next(this.activeRoute, x => !!x)
 
+    rendered = async () => {
+        await this.ready()
+        await this.activeRoute.get().rendered
+    }
+
     /** @type {Map<string, Route>} */
     history = new Map()