feat: add satellite imagery background

index.html

@@ -56,6 +56,7 @@
             <select id="background-select" name="background">
               <option value="soft">Soft minimal</option>
               <option value="openstreetmap">OpenStreetMap</option>
+              <option value="satellite">Satellite imagery</option>
             </select>
           </label>
         </section>