add auto generating changlog to workflow

[joshlynchONS]

Added code for an auto generating changelog to the workflow.

Checklists

This pull/merge request meets the following requirements:

• [ ] code runs
• [ ] developments are ethical and secure
• [ ] you have made proportionate checks that the code works correctly
• [ ] you have tested the build of the template
• [ ] test suite passes
• [ ] minimum usable documentation written in the docs folder

Comments have been added below around the incomplete checks.