Add changelog

[xmunoz]

Looks like you just pushed a major version bump. It would be really helpful for users of this package if you published a changelog along with version bumps so that users can know what to expect :)

[dougalg-js-tw]

Came here to look for the changelog, and scanned the commit history, and it's not clear to me why it moved a major version. I want to upgrade, but don't want to break anything inadvertently.