add bmc widget for index page

templates/index.html

@@ -130,6 +130,8 @@ <h1 class="leaflet-sidebar-header">Profile<div class="leaflet-sidebar-close"><i
     <div id="map" style="height: 100vh;"></div>
 
     <script src="{{ url_for('static', filename='js/visualizer.js') }}"></script>
+
+    <script data-name="BMC-Widget" data-cfasync="false" src="https://cdnjs.buymeacoffee.com/1.0.0/widget.prod.min.js" data-id="oskarkraemer" data-description="Support me on Buy me a coffee!" data-message="Help me to cover server costs. Thank you for your support 😊" data-color="#FF813F" data-position="Right" data-x_margin="18" data-y_margin="18"></script>
 
 </body>
 </html>