Housekeeping and adding Rapperswil Software Crafters

[marcokuoni]

• We will soon start a Software Crafters group in Rapperswil, Switzerland.
• I also did some housekeeping and added Nix. Check out the commit messages.
• To clarify: the website currently includes JavaScript and CSS both in index.html and through Packagist for mapbox. So they are being loaded twice. I tried to fix this, but it turns out the two CSS files are slightly different, which broke the popup. Also, the JavaScript expects MapboxGeocoder to be available in the global scope, which no longer works if we remove the script tags from index.html. I’ve reverted the commit and adjusted the CSS inclusion for now. I recommend updating Mapbox to the latest major release and cleaning up the integration properly.