Npm publish

Summary:This work allows automated release deployment.

Previous semi-automation lived in release.sh and I split it into two pieces:
- test-manual-e2e.sh - that just tests that current commit is buildable and makes a quick e2e installation for manual testing
- publish-npm.js - that makes publish based on what current branch and tags are on commit that is tested/deployed by CI

This simplified `Releases.md` guide and requires you to just run
```
git checkout -b 0.22-stable
git tag v0.22.0-rc
git push origin 0.22-stable --tags
```
to have a successful npm release.
Closes https://github.com/facebook/react-native/pull/6453

Reviewed By: mkonicek

Differential Revision: D3047938

Pulled By: bestander

fb-gh-sync-id: dbebf4c3a0bc2c2a0ef75c54595ab5654f91b8ea
shipit-source-id: dbebf4c3a0bc2c2a0ef75c54595ab5654f91b8ea