doc: change color of doctag on night mode

Fixes: #38641

PR-URL: #38652
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Derek Lewis <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Zijian Liu <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: Ayase-252

doc/api_assets/hljs.css

@@ -36,7 +36,8 @@
 }
 
 .dark-mode .hljs-keyword,
-.dark-mode .hljs-attribute {
+.dark-mode .hljs-attribute,
+.dark-mode .hljs-doctag {
   color: #66d9ef;
 }