Support private repo release

[HananoshikaYomaru]

Support private repo release

[TfTHacker]

This is beyond the scope of what I plan to implement with BRAT. PR's welcome :-)

Unless there is an easy way to do it without authentication (which I don't want to build into BRAT).

[HananoshikaYomaru]

I think you don't need to build the whole github authentication into BRAT, all you need is just a personal access token.

if you want to do it, I guess you reopen this issue and I will see if I have time to do it someday.