Adds a simple json quasiquoter thingy.
Json can be sent to the `/mailfilter?action=update` endpoint.
Change-Id: Iba80c2ab69178e431519933c4a01cd68aaa9f637
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7839
Tested-by: BuildkiteCI
Autosubmit: Profpatsch <mail@profpatsch.de>
Reviewed-by: Profpatsch <mail@profpatsch.de>
