[Docs Site] Add styleGuide frontmatter to GitHubCode docs (#23538)

Author: KianNH

src/content/docs/style-guide/components/github-code.mdx

@@ -1,5 +1,7 @@
 ---
 title: GitHubCode
+styleGuide:
+  component: GitHubCode
 ---
 
 import { GitHubCode } from "~/components";