Mark this repository as unmaintained

[ejcoyle88]

Hi, obviously I've left EKM a while ago, and no one seems to be looking after this. There's a fair few issues getting opened, so it would probably be a good idea for someone to mark this repo as unmaintained so people know not to use the package (and the issues also stop pinging my email 😹 ). @ ing a few people from EKM to hopefully get a notification to land somewhere.

@jackcaldwell @simax @nickstansfield