add artplayer-plugin-vtt-thumbnail

package.json

@@ -64,4 +64,4 @@
         "prettier"
     ],
     "__npminstall_done": false
-}
+}

packages/artplayer-plugin-vtt-thumbnail/package.json

@@ -21,4 +21,4 @@
         "video",
         "player"
     ]
-}
+}