Create CHANGELOG.md

[glen-cheney]

Hey there 👋

Thanks for this package! My team at Lyft uses it in our request library. We're currently on v1 and looking to upgrade to the latest version. Since you don't have a changelog, it's hard for us to know what actions would need to be taken to update our usages.

So, I created a CHANGELOG.md based on the commit history to help others coming back and looking to upgrade their versions.

[iambumblehead]

@vestride thank you for this kind contribution. I'm learning about github actions and releases at this repository https://github.com/iambumblehead/esmock and am planning to duplicate the release model of that package here soon and will plan to keep the CHANGELOG added here up to date

Thank you

[iambumblehead]

@vestride thank you I've already added a few points to the changelog