Add Xandikos to list of software that provides /metrics without a separate exporter. (#1509)
Add Xandikos to list of software that provides /metrics without a separate exporter. (#1509)

Signed-Off-By: Jelmer Vernooĳ <9648816b5a0c45426c88e14104568baf9283dd28@jelmer.uk>
prometheus/docs,prometheus/docs,prometheus/docs