Issue #600: fix DOM mutation issue regarding vue in-place-patching tickets for components audio and video.

nicegui/elements/audio.js

@@ -1,9 +1,5 @@
 export default {
-  template: `
-    <audio :controls="this.controls" :autoplay="this.autoplay" :muted="this.muted">
-      <source :src="this.src" :type="this.type">
-    </audio>
-  `,
+  template: `<audio :controls="controls" :autoplay="autoplay" :muted="muted" :src="src" :type="type"/>`,
   props: {
     controls: Boolean,
     autoplay: Boolean,

nicegui/elements/video.js

@@ -1,9 +1,5 @@
 export default {
-  template: `
-    <video :controls="this.controls" :autoplay="this.autoplay" :muted="this.muted">
-      <source :src="this.src" :type="this.type">
-    </video>
-  `,
+  template: `<video ref="videoPlayer" :controls="controls" :autoplay="autoplay" :muted="muted" :src="src" :type="type" />`,
   props: {
     controls: Boolean,
     autoplay: Boolean,