Trigger export over json protocol from the ui

[dschmidt]

• [x] I agree to follow the Code of Conduct that this project adheres to.
• [x] I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Is your feature request related to a problem? Please describe. I would like to handle an export triggered in the ui in my hosting application. AFAICT from reading the documentation it's possible to trigger an export via the json protocol and then have the data be sent via the json protocol but it's not possible for the user to trigger this from the regular export ui.

Describe the solution you'd like User can click File -> Export -> $format and when clicking export my host application can provide a saving dialog. Of course this could or should be opt in.

Describe alternatives you've considered Don't implement it

Additional context