Add a Troubleshooting section to GitHub Educator Verification page

[Jacqueline Russell]

Hi Galen,
We've had a lot of support questions about the GitHub Educator verification process.
Let's document some additional information that we can point people to on this page: https://makecode.com/github-teacher-verification

At the very bottom, let's add a new "Support and Frequently Asked Questions" section with the following information:

• It won’t verify me, what can I do?
  GitHub has been able to successfully verify the academic affiliation of more than one hundred thousand educators worldwide - we are confident we can do the same for you! If you are unable to be verified, make sure to address all of the specific reasons presented to you by the app.

• I don’t have a .edu email address, can I still get verified?
  If your school provides academic email then you will be required to use it. If not, then capturing an image of official dated proof of your current academic affiliation and following the app's instructions should be enough to get you verified.

• I was verified, but now I’m not. What happened?
  GitHub periodically requires re-verification of all of our academic users. GitHub sends notifications to users in advance of the required re-verification deadline, so check your GitHub notification settings if your status changed without your knowledge.

• I don’t have a GitHub account, and don’t use GitHub for anything else. Can I get verified without creating a GitHub account?
  Sorry, no :-(. But non-programmers can benefit from having a GitHub account! Please visit https://education.github.com/teachers to learn more.

• I'm still having issues, how can I get help?
  Try posting your question to the GitHub Education Community Forum. There are many people who can help you there!
  If there is a technical issue, or there is incorrect school information listed, please contact GitHub Education Support.

Thanks!