README: add trailing slash to homepage

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

README

@@ -79,7 +79,7 @@ the http-headers "Modified" and "Expires".
 
 Online presence
 
-* The cgit homepage is hosted by cgit at <http://git.zx2c4.com/cgit/about>
+* The cgit homepage is hosted by cgit at <http://git.zx2c4.com/cgit/about/>
 
 * Patches, bugreports, discussions and support should go to the cgit
   mailing list: <cgit@lists.zx2c4.com>. To sign up, visit