Implement caching for feature collections (#30) and maps (#4).

src/Netzmacht/Contao/Leaflet/DependencyInjection/LeafletServices.php

@@ -10,6 +10,7 @@
 
 namespace Netzmacht\Contao\Leaflet\DependencyInjection;
 
+use Doctrine\Common\Cache\Cache;
 use Netzmacht\Contao\Leaflet\Boot;
 use Netzmacht\Contao\Leaflet\Frontend\ValueFilter;
 use Netzmacht\Contao\Leaflet\Mapper\DefinitionMapper;
@@ -40,6 +41,13 @@ class LeafletServices
      */
     const BOOT = 'leaflet.boot';
 
+    /**
+     * Leaflet cache
+     *
+     * @return Cache
+     */
+    const CACHE = 'leaflet.cache';
+
     /**
      * Service name of the definition builder.
      *