Ability to add additional containers to Pihole pod

[kenlasko]

I have a script that watches the pihole.log for specific DNS queries which then triggers a webhook to Home Assistant. This script runs in a separate container within the Pihole pod and uses a shared volume against /var/log/pihole. I tried to use the extraObjects section to add an additional container, but could not get it to work.

I propose adding an extraContainers section to the values.yaml which will allow for the addition of additional containers within the Pihole pod.

I could also take a stab at adding this functionality myself, but I'm pretty new to Helm and properly using GitHub as well.

[kenlasko]

I did take a stab at it:
#260