Default pull request template

[jackzhxng]

🚀 The feature, motivation and pitch

Create a pull request template to encourage more descriptive PRs and facilitate release note aggregation.

Alternatives

N/A

Additional context

N/A

RFC (Optional)

No response

[iseeyuan]

Good call! @dvorjackz could you help on this? There may be the template in pytorch core that we can leverage.