add autoHeight option

packages/artplayer/src/player/autoHeightMix.js

@@ -0,0 +1,25 @@
+import { setStyle, hasClass, addClass, removeClass, def } from '../utils';
+
+export default function autoHeightMix(art, player) {
+    const { $container, $video } = art.template;
+
+    def(player, 'autoHeight', {
+        get() {
+            return hasClass($container, 'art-auto-height');
+        },
+        set(value) {
+            if (value) {
+                const { clientWidth } = $container;
+                const { videoHeight, videoWidth } = $video;
+                const height = videoHeight * (clientWidth / videoWidth) + 'px';
+                setStyle($container, 'height', height);
+                addClass($container, 'art-auto-height');
+                art.emit('autoHeight', height);
+            } else {
+                setStyle($container, 'height', null);
+                removeClass($container, 'art-auto-size');
+                art.emit('autoHeight');
+            }
+        },
+    });
+}