Enable keyboard pan+zoom using tabindex

Author: simon04

index.html

@@ -14,7 +14,7 @@
     <textarea id="mapcss"></textarea>
     <button id="executeQuery">Execute Overpass QL</button>
     <button id="executeStyle">Execute MapCSS</button>
-    <div id="map"></div>
+    <div id="map" tabindex="0"></div>
     <script type="module" src="./src/main.ts"></script>
   </body>
 </html>