RFE: Bug tracking system preference

Please mention your bug tracking system preference.

https://www.sudo.ws/docs/contributing/#filing-bug-reportsissues and

sudo/docs/CONTRIBUTING.md

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## Filing bug reports/issues

don't match with

sudo/README.md

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## Bug reports

Those documents both mention bugzilla and GitHub so I don't really see the problem.

But not in the same order so I'm wondering which one do you prefer.

BTW, first ones mention e-mail too.

I've made the two bug reporting sections consistent now. It doesn't really matter to me whether people report bugs in bugzilla or GitHub. I've run the bugzilla instance for a very long time but filing a bug requires making an account so using GitHub is simpler for people who already have a GitHub account.