feat: Add artplayer-plugin-auto-thumbnail plugin

docs/assets/example/auto.thumbnail.js

@@ -0,0 +1,14 @@
+// npm i artplayer-plugin-auto-thumbnail
+// import artplayerPluginAutoThumbnail from 'artplayer-plugin-auto-thumbnail';
+
+var art = new Artplayer({
+    container: '.artplayer-app',
+    url: '/assets/sample/video.mp4',
+    plugins: [
+        artplayerPluginAutoThumbnail({
+            width: 160,
+            number: 100,
+            scale: 1,
+        }),
+    ],
+});