add auto pip mode

packages/artplayer/src/plugins/autoPip.js

@@ -0,0 +1,14 @@
+import { debounce } from '../utils';
+
+export default function autoPip(art) {
+    const { events, player, template } = art;
+    const scrollDebounce = debounce(() => {
+        const { top, height } = template.$player.getBoundingClientRect();
+        if (top + height <= 0 && !player.pip && player.playing) {
+            player.pip = true;
+        } else if (player.pip) {
+            player.pip = false;
+        }
+    }, 300);
+    events.proxy(window, 'scroll', scrollDebounce);
+}