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/components/api-service/embed-modal/index.less

@@ -4,5 +4,5 @@
 
 .codeText {
   padding: 10px;
-  background-color: #e8e8ea;
+  background-color: #ffffff09;
 }