add maplibre spec link (#463)

TODO: would be great to introduce a proper tile spec section, just like other primary projects

Author: nyurik

src/pages/index.astro

@@ -337,6 +337,11 @@ import { SITE_DESCRIPTION } from "../constants";
                   >Awesome MapLibre on GitHub</a
                 >
               </li>
+              <li>
+                <a href="https://maplibre.org/maplibre-tile-spec"
+                  >MapLibre Tile Specification</a
+                >
+              </li>
               <li>
                 <a href="https://github.com/maplibre"
                   >All MapLibre GitHub repositories</a