Add a changelog.rst file

[cristiansteib]

I think it could be good for the whole community to know what changes are involved in every release. Could you consider adding a changelog.rst file at the top of the repository.

This https://changelog.md/ is a good changelog standard. If you consider this, also consider that every pull request must include the changes in the changelog.rst.

[alanjds]

Yeah, I considered this more than once.

Researched more than one tool, even automated ones, and found that I like the way https://pypi.org/project/towncrier/ works. Yet had not enforced something like this.

[gdvalderrama]

This is actually requested here https://github.com/alanjds/drf-nested-routers/issues/113 It'd be nice to have at least a basic changelog to start if figuring out of to automate it is too time consuming