UI element to view changes in draft

[effigies]

Is your feature request related to a problem? Please describe.

User story: A user makes several changes to a dataset, losing track of the full set of changes made. They want to see a comparison between the latest snapshot and the current draft, to decide if they have made all (and only) the changes they want for a new snapshot.

Describe the solution you'd like

A UI page for viewing the changes to the dataset, roughly along the lines of GitHub's compare/1.0.0...main. Being able to compare to other snapshots would be a bonus.

Describe alternatives you've considered

The current alternative is to use git diff on the datalad dataset cloned from the private URL or download two copies with the CLI and diff them, laid out in https://gist.github.com/effigies/312d615f78bc2ce1543be7b514a924af.

Additional context

With the data retention policy going into effect, this functionality may have many potential users.