fix(bgsize): 修复bgsize兼容问题

app/web/page/mixins/transformStyle.mixin.ts

@@ -9,7 +9,7 @@ export default class TransformStyleMixin extends Vue {
   transformStyle(styleObj, point = {}, name) {
     const style = {
       backgroundRepeat: 'no-repeat',
-      backgroundSize: 'cover'
+      backgroundSize: '100% auto'
     };
     if (!styleObj) { return style; }
     for (const key of Object.keys(styleObj)) {