feat(#12): add a preconnect information for youtube video if used

Author: peterpeterparker

src/components/extra/deckdeckgo-youtube/deckdeckgo-youtube.tsx

@@ -15,9 +15,35 @@ export class DeckdeckgoYoutube {
   @Prop() height: number;
 
   async componentDidLoad() {
+    await this.addPreconnectLink();
+
     await this.createIFrame();
   }
 
+  private addPreconnectLink(): Promise<void> {
+    return new Promise<void>((resolve) => {
+      if (!this.src) {
+        resolve();
+        return;
+      }
+
+      const links: NodeListOf<HTMLElement> = document.head.querySelectorAll('link[rel=\'preconnect\']');
+
+      if (links && links.length > 0) {
+        resolve();
+        return;
+      }
+
+      const link: HTMLLinkElement = document.createElement('link');
+      link.rel = 'preconnect';
+      link.href = 'https://www.youtube.com';
+
+      document.head.appendChild(link);
+
+      resolve();
+    });
+  }
+
   @Method()
   async updateIFrame(width: number, height: number) {
     const iframe: HTMLIFrameElement = this.el.shadowRoot.querySelector('iframe');