Add conventional changelogs

[josgraha]

As a user I would like to see CHANGELOG.md in a format that maps features / fixes etc to commits. This is possible with the Conventional Changelog

Here is an example

[josgraha]

not sure if i should start at the API level reason-glfw and reason-sdl2 or go top down and start here

[szbergeron]

not sure if i should start at the API level reason-glfw and reason-sdl2 or go top down and start here

Hi, most of the development and tooling for reason-sdl2 was actually completed by @bryphe, so I'm not super familiar with how I'd add it there. Changelogs for Revery (I thought) were already somewhat present, but I haven't looked into it all that much.

[josgraha]

thanks @szbergeron, i was over-optimistically hoping i could get commitlint and standard-version working, but I have run into some issues with git hooks and commitlint with esy, we can however bring in standard-version to generate a nice CHANGELOG.md