please allow so set custom UID & GID from VEN'S

[zubziro1]

allow to customize startup container to run as user & group of choice. Like :
containers:
- env:
- name: PUID
value: '1001'
- name: PGID
value: '1002'
Default 1000: 1000 is not suitable in all situations.

[gizmocuz]

That is needed by some hardware.
If you want you can make a PR