Add NET_ADMIN to pihole about casaos-appstore

[ETWang1991]

1. 是否需要仅开发者模式下提供这一修改项
   whether the modifier should be available in developer mode only
2. 修改项是否放在Docker设置里
   whether the modifications are placed in Docker settings

[EthraZa]

Pi-hole does need NET_ADMIN, but it will only work as DHCP server if using network HOST, otherwise it needs a DHCP relay container (set as network host) like: DHCP-Relay.