Add netbox documentation to the offical documentation

[scoopex]

See SovereignCloudStack/hardware-landscape#32

To ensure that this documentation can be found or that this MVP can be continued at a later date, it would be good to link this documentation on the documentation page.

In @maxwolfs 's and my opinion, we add a ‘Concepts’ section below https://docs.scs.community/contributor-docs where we add this documentation as a menu item ‘Netbox SONiC Provisioning’.

[scoopex]

https://github.com/SovereignCloudStack/hardware-landscape/blob/main/documentation/sonic/Provisioning.md
https://github.com/SovereignCloudStack/hardware-landscape/blob/main/documentation/sonic/ONIE.md
https://github.com/SovereignCloudStack/hardware-landscape/blob/main/documentation/sonic/ZTP.md