Output @names

[dblock]

Provide a separate output with just the @NAMEs so they can be @mentioned.

[dbwiddis]

To clarify this, the existing output does have the username at the beginning, so it's less providing the output as coordinating this output and #27. Here's a sample output for a user (obfuscated):

someuser: Some User <54680617+someuser@users.noreply.github.com>, someuser <someuser@gmail.com>

In this case, I have at least one valid email address, so it should just remove the noreply one:

someuser: someuser <someuser@gmail.com>

However, in the case where there are no valid email addresses, the @ output is useful to add, such as these two usecases:

anotheruser: 
user2019: user2019 <53431879+user2019@users.noreply.github.com>