Update demo.html

[d3liaa]

I updated the script link with the one found in the web component store, because with the present one, it doesn't work.

[dulvui]

I checked now and it works (except that I can't see the map in the background) when you do:

npm install
npm run start

With this steps you create the necessary files in the .dist folder

[d3liaa]

I only checked for when you implement the webcomponent in a website, and with the new script the demo worked.