Add Dark Peak Data Co-operative to the directory.

Signed-off-by: Mat Booth <mbooth@apache.org>

directory.json

 {
 "aktivix.org" : "https://aktivix.org/librehost.json",
+"Dark Peak Data Co-operative" : "http://librehosters-api.darkpeak.org/librehost.json",
 "Disroot.org" : "https://disroot.org/librehost/librehost.json",
 "hackerspaces.be" : "https://hackerspaces.be/librehost.json",
 "Indie.Host" : "https://indie.host/librehost.json",