pobradovic08

Fixes #22 in the simplest way by just adding the missing `ipam.vlan_group` object (from already imported `vlan_group` class).

### NetBox Python version v0.1.6 ### NetBox version v3.6.6 ### Python version 3.11 ### Steps to Reproduce Trying to call: ``` self.api.ipam.vlan_group.available_vlans.list(id=group_id, limit=1) ``` or ``` self.api.ipam.vlan_groups.available_vlans.list(id=group_id, limit=1) ``` Fails...