Update README.md

Co-authored-by: Sandro <sandro.jaeckel@gmail.com>

README.md

@@ -223,8 +223,8 @@ Some commands (i.e., `post-result` or `merge`) require a GitHub API token, and
 even for read-only calls, GitHub returns 403 error messages if your IP hits the
 rate limit for unauthenticated calls.
 
-Nixpkgs-review will automatically read the oauth_token stored by [hub][1] or
-[gh][2] if they are installed.
+Nixpkgs-review will automatically read the oauth_token stored by [hub](https://hub.github.com/) or
+[gh](https://cli.github.com/) if they are installed.
 
 Otherwise, you'll have to create a "personal access token (classic)" through
 GitHub's website. See [the GitHub documentation][3] for instructions. If you