Automatically generate list of locations from events.json

[ChristophMuth]

The events.json file contains all the information needed for the map popup. It needs to be enriched by the geocoordinates using the address data.

Instead of having to manually create the locations array (locations.js) file, we could retrieve the lat/long coordinates from a geocode api like geoapify.

[McPringle]

One nice way would be to add this functionality in the gulpfile.js. Parse the events.json and create something like locations.json. Take a look at generating the feed.xml in the same file. It parses the events.json and creates a XML file.

[BeniRupp]

We started implementing this feature on yesterday's Hackergarten in Stuttgart. Hopefully, we can finish this issue in one of the next Hackergarten events. See #435