added chart.js to leaflet.js

public/leaflet-stoeckach-heatdemand/index.html

@@ -11,7 +11,7 @@
     <script src="https://unpkg.com/leaflet@1.7.1/dist/leaflet.js"
         integrity="sha512-XQoYMqMTK8LvdxXYG3nZ448hOEQiglfqkJs1NOQV44cWnUrBc8PkAOcXy20w0vlaXaVUearIOBhiXZ5V3ynxwA=="
         crossorigin=""></script>      
-<script src="building_data.js"></script>
+ <script src="https://cdn.jsdelivr.net/npm/chart.js"></script> 
 <script src="building_data.js"></script>
     <link rel="stylesheet" href="index.css">
         	    <style>