Add shortcut for geocoder search field

Press 'F', type a query and press 'Enter' to find places effortlessly.

Note that the button already triggers on mousedown events, even though
by convention it should react on mouseup (i.e. a regular click)
only. However, that's an issue in the external dependency, and can
be worked around for now.

js/plugin/Search.js

@@ -6,7 +6,10 @@ BR.Search = L.Control.Geocoder.extend({
             }),
             sizeInMeters: 800
         }),
-        position: 'topleft'
+        position: 'topleft',
+        shortcut: {
+            search: 70 // char code for 'f'
+        }
     },
 
     initialize: function(options) {
@@ -16,6 +19,8 @@ BR.Search = L.Control.Geocoder.extend({
             // (e.g. when added directly to "options:" above), so we have to call it here
             placeholder: i18next.t('map.geocoder-placeholder')
         });
+
+        L.DomEvent.addListener(document, 'keydown', this._keydownListener, this);
     },
 
     markGeocode: function(result) {
@@ -38,5 +43,12 @@ BR.Search = L.Control.Geocoder.extend({
         if (this._geocodeMarker) {
             this._map.removeLayer(this._geocodeMarker);
         }
+    },
+
+    _keydownListener: function(e) {
+        if (BR.Util.keyboardShortcutsAllowed(e) && e.keyCode === this.options.shortcut.search) {
+            $('#map .leaflet-control-geocoder')[0].dispatchEvent(new MouseEvent('mousedown'));
+            e.preventDefault();
+        }
     }
 });