chore: capitalize H in GitHub in nav links (#27)

This is my biggest pet peeve on earth 😅Love this project so far, can't wait to try it out on something real!

Author: adamwathan

lib/default-theme/NavLinks.vue

@@ -12,7 +12,7 @@
       class="github-link"
       target="_blank"
       rel="noopener">
-      Github
+      GitHub
       <OutboundLink/>
     </a>
   </nav>