add world editor to React DOM render

[ssube]

Add an editor mode for world templates, using Formik or something similar to build forms and lists.

Template refs should be a dropdown list of the appropriate template type IDs with numeric input. Template numbers should be paired numeric inputs.

The editor should have a form-and-list view, as well as a JSON/YAML view. Edits to one should appear in the other, and the text view should have a validation status indicator. Any schema errors should be shown and prevent switching back to the form-and-list view, if the text view has been edited and is no longer valid.