new preview for office doc

src/views/questioncenter/components/paper-actions-mixin.js

@@ -13,6 +13,8 @@ export default {
       if (this._isPDF(url)) {
         window.open('/pdfView/index.html?src=' + url)
       } else if (this._isOffice(url)) {
+        // https://view.officeapps.live.com/op/view.aspx
+        // https://view.xdocin.com/view
         window.open('https://view.xdocin.com/view?src=' + encodeURIComponent(url))
       } else {
         this.$message.error('格式错误，无法预览该格式文件！');