Theme switch support (#3568)

### What problem does this PR solve?
- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
Co-authored-by: Jin Hai <haijin.chn@gmail.com>

web/src/pages/add-knowledge/components/knowledge-testing/testing-control/index.less

@@ -1,6 +1,6 @@
 .testingControlWrapper {
   width: 350px;
-  background-color: white;
+  background-color: rgba(255, 255, 255, 0.1);
   padding: 30px 20px;
   overflow: auto;
   height: calc(100vh - 160px);