Add changelog option to migrate create command

[coffeemakingtoaster]

Is your proposal related to a problem?

When working with a long running project I always find it frustrating when there are no migration changelogs. Depending on the circumstances this requires me to go to the PR introducing the migration to find a list of changes (if that even exists).

Describe the solution you'd like

An easy solution to this would be to introduce an --generate-changelog flag to the hasura migrate create command. When provided with that flag the generated folder with the migration could also contain a template changelog.md.
The developer can then specify the changes made with the migration within said changelog file.
An example template could look like this:

Changelog

Breaking changes

• change 1
• change 2

Non breaking changes

• change 3

If the feature is approved, would you be willing to submit a PR?

If the feature is approved I feel like this would be a good opportunity to contribute, so yes I would submit a PR.