Berlin Gathering

[yuhattor]

Moved from #122

[yuhattor]

@MaineC I moved PR from forked repo to here!
Also I updated with basic minimal setup.
Could you edit data/en/xxx.yaml files?

[MaineC]

I think we will need some sort of https://de.wikipedia.org/wiki/Impressum for the site. Not sure which information to put in there. As an example, this is the FOSS Backstage page: https://25.foss-backstage.de/imprint/

Ticket sales will be handled through the FOSS Backstage ticket shop. There will be a URL where you can buy tickets only for the gathering. I'll add that one as soon as I have it. Tickets will also be available as an add-on to a regular Backstage ticket.

Apart from that I hopefully captured all of the modifications that needed to be made.

[MaineC]

Also: Thank you for moving the content into the regular gatherings template! I was totally lost on which content should go where in the data files ;) Need to learn Japanese at some point I guess.