Circle CI: Create GiHub Release draft when bumping version

Summary:
Automatically create a GitHub Release draft when a new React Native release is created.

The GitHub Release will be created by the same Circle CI job that publishes the package to npm.

This job will also upload the built Hermes binaries to the GitHub release.

Changelog: [Internal]

Reviewed By: cipolleschi

Differential Revision: D36646696

fbshipit-source-id: 0a863dc4e3215fc95f7852f8dc43858cdd852aaa