Update conferences.md

[mhibino]

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. If you've added code that should be tested, add tests!
3. If you've changed APIs, update the documentation.
4. Ensure the test suite passes (npm test).
5. Format your code with prettier (npm run prettier).
6. Make sure your code lints (npm run lint).
7. Run the Flow typechecks (npm run flow).
8. If you added or removed any tests, run ./scripts/fiber/record-tests before submitting the pull request, and commit the resulting changes.
9. If you haven't already, complete the CLA.

[aweary]

Thanks, I heard it was a great conference!