Add a changelog for major features and breaking changes

[j6k4m8]

It would be great to have a changelog in this repo in order to notate when large features are added or breaking changes are introduced.

(My use case: nbterm --version shows me 0.0.7, latest is 0.0.10 — is it worth updating?)

[davidbrochart]

Although it's still very early stage, I agree I need to start a changelog. It's always worth updating because there is a lot left to do and it's evolving fast.

[j6k4m8]

I definitely don't mean to just add more work to your plate :) If I had more awareness of what those features are, I would have made this a PR instead of an issue, I promise :)