doc: add backtop

Author: tangjinzhou

site/index.html

@@ -66,12 +66,12 @@
     <div
       class="surveybyantdv"
       data-sf-id="63ad5912f3e10066"
-      data-sf-mode="sidetab"
+      data-sf-mode="popover"
       data-sf-button-color="#1890ff"
       data-sf-text-color="#ffffff"
       data-sf-font-size="18"
-      data-sf-button-text="体验反馈"
-      data-sf-button-radius="4"
+      data-sf-button-text=""
+      data-sf-button-radius="50%"
       data-sf-button-icon="like-outlined"
       data-sf-default-open="false"
       data-sf-allow-repeat-submit="true"

site/src/layouts/index.vue

@@ -59,6 +59,7 @@
             </a-anchor>
           </a-affix>
         </section>
+        <a-back-top />
         <div class="fixed-widgets" :style="isZhCN ? { bottom: '175px' } : {}">
           <a-dropdown placement="top">
             <template #overlay>

site/src/theme/static/common.less

@@ -205,7 +205,7 @@ a {
   position: fixed;
   right: 32px;
   bottom: 102px;
-  z-index: 2147483640;
+  z-index: 100;
   display: flex;
   flex-direction: column;
   cursor: pointer;