Set-up CI for ohdear-system-health to build binaries automatically as artefacts

[derickr]

The monitoring uses https://github.com/derickr/ohdear-system-health, and our playbook installOhDear.yml currently has a task to pull the used binary from https://derickrethans.nl/files/dump/ohdear-system-health.

Set up a CI pipeline on https://github.com/derickr/ohdear-system-health to build a binary there automatically when a new release is made, and change the playbook to use the latest binary from there.