feat: change the util component of code block to default semi-transparent, and become opaque when hovering (#183)

src/content-script/styles.scss

@@ -120,6 +120,12 @@
     position: absolute;
     right: 10px;
     top: 3px;
+    transition: opacity 0.3s;
+    opacity: 0.2;
+  }
+
+  .code-corner-util:hover {
+    opacity: 1;
   }
 
   .gpt-util-group {