Add 'Last Edited' Section to Observation Fields

Platform(s): website

Description of need:
Anyone can edit an observation field (unless restricted by the observer), but currently it only displays who added the field. It can be hard to tell if the field’s value is the original or if it has been edited by someone. If someone wanted to thank who updated the field or ask why they chose that specific value (like prey ID or feather placement), they might end up asking wrong person.

Feature request details:
I propose a new section ‘Last Edited’ to be added (since I think a history section like the taxon pages would be too much).
158
This should help with above situations as well as with this bug: https://forum.inaturalist.org/t/adding-or-editing-observation-fields-reports-wrong-user/2290.