A shoved handler to receive notifications from Matrix.
To set up, run
./register.sh HOMESERVER_URL ACCESS_TOKEN, replacing those values
Note: shoved-matrix currently only supports one account.
Another note: Matrix servers do not natively support Web Push, so shoved-matrix routes notifications through my server (push.chat.vpzom.click). This server will see the event and room IDs for the notifications, but not their content. If you wish, you can replace this with your own server running Sygnal in register.sh.