Basic leaflet example shamelessly stolen from various places on the web.

public/index.html

@@ -22,6 +22,13 @@
     <meta name="apple-mobile-web-app-capable" content="yes" />
     <meta name="apple-mobile-web-app-title" content="Ionic App" />
     <meta name="apple-mobile-web-app-status-bar-style" content="black" />
+
+    <!-- Leaflet -->
+    <link rel="stylesheet" href="https://unpkg.com/leaflet/dist/leaflet.css" />
+    <link
+            rel="stylesheet"
+            href="https://unpkg.com/react-leaflet-markercluster/dist/styles.min.css"
+    />
   </head>
 
   <body>