fix(website): CSS of jest card (#12127)

Author: ony3000

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - `[babel-jest]` Add `process.version` chunk to the cache key ([#12122](https://github.com/facebook/jest/pull/12122))
+- `[website]` Fix the card front that looks overlapping part of the card back
 
 ### Chore & Maintenance
 

website/static/css/custom.css

@@ -123,6 +123,7 @@ div.jest-card-front,
 }
 
 div.jest-card-front {
+  z-index: 1;
   background-color: #fff;
   border: 1px solid #bbb;
 }