Add US Military emails to github government

[david-saeger]

Is your feature request related to a problem? Please describe the problem you're trying to solve.

I dont see mail.mil as an approved domain for granting access to github government

Describe the solution you'd like

Id like to add mail.mil and dds.mil to the list of domains here https://github.com/benbalter/gman/blob/master/config/domains.txt

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.