feat: Add network override CLI option

[popey]

Expected behavior

Sometimes I'd like to override the network behaviour of quickemu. Specifically I'd like to disconnect the network, or change to a bridged network.

Something like this:

quickemu --network none

or

quickemu --network bridged

Actual behavior

There's no option to do this.

Thanks!

[flexiondotorg]

From talking with you, I think all you really care about is configuring an offline state.

How does this sound? I'm just going to add a --offline argument, which overrides any network configuration with none.