Add maptiler logo (#473)

Author: mpfeil

app/components/leaflet.directive.html

@@ -1 +1,4 @@
-<div class="leaflet-map"><div ng-transclude></div></div>
+<div class="leaflet-map">
+    <a href="https://www.maptiler.com" style="position:absolute;right:10px;bottom:20px;z-index:999;"><img src="https://api.maptiler.com/resources/logo.svg" alt="MapTiler logo"></a>
+    <div ng-transclude></div>
+</div>