NetBox plugin 1.0.0

First release. Special agent and check plugins to monitor a NetBox 4.x
installation from Checkmk 2.5.0.

Centred on NetBox's quietest failure mode: with no RQ worker running, data source
syncs, custom scripts, event rules and bulk operations silently stop while the
web UI stays perfectly responsive.

15 services. See CHANGELOG.md for the full list.