Migrate to new GitHub issue templates

Summary:
This will allow us to present a user with a different template depending on the type of help they need.

To do:

1. Update the bot so that it auto-closes any issue that contains text from `question.md` (i.e. tried to ask a question through GitHub).
2. In a separate PR: new template to handle feature requests (update the bot to allow these to remain open)
3. Allow multiple other types of issues, such as requesting a cherry pick, or reporting a regression vs. something that does not work as expected.
4. Link to Stack Overflow / Discuss directly if and when GitHub allows the 'Get Started' button to point to a URL.
Closes https://github.com/facebook/react-native/pull/19334

Differential Revision: D8051229

Pulled By: hramos

fbshipit-source-id: 9e8aea232688c53dcbb0c047e92799e68b8b7842