Make preview useable offline by adding explicit protocoll for leaflet…

… files

preview/index.html

@@ -6,7 +6,7 @@
 	<meta name="viewport" content="width=device-width, initial-scale=1.0">
 	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 
-	<link rel="stylesheet" href="//unpkg.com/[email protected]/dist/leaflet.css" />
+	<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" />
 
 	<style>
 		html {
@@ -77,7 +77,7 @@ <h4><a href="https://github.com/leaflet-extras/leaflet-providers">Leaflet-provid
 	</div>
 	<div id="map" class="map"></div>
 
-	<script src="//unpkg.com/[email protected]/dist/leaflet.js"></script>
+	<script src="https://unpkg.com/[email protected]/dist/leaflet.js"></script>
 	<script src="../leaflet-providers.js"></script>
 
 	<script src="vendor/L.Control.Layers.Minimap.js"></script>