[BUG] OpenBSD - ifconfig(8) support

[ghost]

Bug description

protonvpn-cli-ng requires ip(8) and doesn't support ifconfig(8), thus not supporting OpenBSD.

To Reproduce

Steps to reproduce:

1. Install protonvpn-cli 2.2.0, as root, via pip3.
2. Run doas protonvpn init
3. See error

Expected behavior

protonvpn 2.0 should connect to the ProtonVPN servers via ifconfig(8)

Error Messages/Program Output/Log Messages (~/.pvpn-cli/pvpn-cli.log)

doas protonvpn init
'ip' not found.
Please install ip.

Desktop (please complete the following information):

• OS: [OpenBSD 6.6 (-STABLE)]
• Python Version: [3.7.4]
• ProtonVPN-CLI Version: [2.2.0]

[SteveClement]

I would argue this applies to more than OpenBSD, older (LTS) Linux systems will not have IP out of the box.
This is a matter of a simple RegEX addition, thus PR please ;)

[Rafficer]

I'll close this in favor of #111. So for further discussion, please go there. :)