Consider a pull request template for breaking changes

[paddyroddy]

Is Your Feature Request Related to a Problem? Please Describe

Making releases (#390) are hard currently due to the need to inform users about possible breaking changes, as the API isn't guaranteed to be backwards compatible. Is there a way we could improve PRs so that making the necessary CHANGELOG would be easy in future?

Describe the Solution You'd Like

No response

Describe Alternatives You've Considered

No response

Additional Context

No response

[Saransh-cpp]

One thing that we do at PyBaMM is make developers add a CHANGELOG note in every PR that introduces a user facing change. Should we do that in GLASS as well, or should I just add a PR template that makes it easier for developers to write what user-facing change this PR is adding?

cc: @ntessore

[paddyroddy]

I guess it would be good to document what we want in this. Some thoughts:

• Is your code passing linting?
• Is your code passing tests?
• Have you written tests if it's a new feature?
• Have you modified/extended the documentation?
• Are you adding a public function which should be exposed in sphinx?