Refresh the New Issue template (#41800)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/41800

I've cleaned up the new issue template:
1. Added Expo to the template selector list
2. Added a short blurb with relevant links at the beginning of every issue template
3. I've added a dedicated field for reproducer and one for extra
4. I've added rendering to the react-native info block
5. I've added another rendered blog for stacktraces.
6. I've added a drop-down item for affected platform

Changelog:
[Internal] [Changed] - Refresh the New Issue template

Reviewed By: GijsWeterings

Differential Revision: D51847659

fbshipit-source-id: 565a2dcab4913825f441e2315ae9b4dd34fd2f4f