Hack days (36): PoC of generating source maps

[jamesvidler]

See https://docs.google.com/document/d/1iqd_oyvC-gigP3knw7TIkMJ4L_QO_dqDbusQ_dQ78-s/edit

WHY are these changes introduced?

Fixes #0000

WHAT is this pull request doing?

How to test your changes?

Post-release steps

Measuring impact

How do we know this change was effective? Please choose one:

• [ ] n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• [ ] Existing analytics will cater for this addition
• [ ] PR includes analytics changes to measure impact

Checklist

• [ ] I've considered possible cross-platform impacts (Mac, Linux, Windows)
• [ ] I've considered possible documentation changes