Proxmox VE: enable TUN/TAP on LXC

This is more of a personal note for myself -- rather than a so-called 'mental note' -- on how to enable TUN/TAP for LXC containers.

There are two options. One can either edit the configuration found in /etc/pve/lxc, in my case this would be 100.conf. The other options is to edit the configuration at /etc/lxc/default.conf and this will apply the newly added settings globally rather than per CT. In my case I do per CT configuration.
I don't add anything in /var/lib/lxc/<my-ct.conf because it will be overwritten on the next start -- so in order to make sure the changes stick I'm always editing the configuration located in /etc/pve/lxc.
Now in order to enable TUN/TAP the following line has to be added to the configuration file:

lxc.cgroup.devices.allow = c 10:200 rwm  

That is all.