Add query param to close sidebar

The sidebar is open by default on large devices, but now we can link to
a fullscreen map for a more immersive experience.

Requested-By: Eric Villnow <eric@vill.now>

main.js

@@ -153,6 +153,10 @@ for (let category of layerCategories) {
     }
   }
 }
+const sidebarVisible = ('sidebar' in urlParams) ? (urlParams.sidebar !== 'false') : true;
+if (!sidebarVisible) {
+  document.body.classList.remove("nav-open");
+}
 
 const customLayerDiv = document.createElement("div");
 customLayerDiv.innerHTML = `