Missing config schema for field formatter third party settings (field.formatter.third_party.sdc_display)

Problem/Motivation

sdc_display stores its settings on individual field formatters via hook_field_formatter_third_party_settings_form(), but config/schema/sdc_display.schema.yml only declares core.entity_view_display.*.*.*.third_party.sdc_display.
Drupal core expects field-formatter third party settings to be described under the schema id field.formatter.third_party.<module> (see core/config/schema/core.entity.schema.yml).

Result Config Inspector / the schema checker reports missing schema for every entry like: core.entity_view_display.<entity_type>.<bundle>.<view_mode>.content.<field>.third_party_settings.sdc_display

Steps to reproduce

Install sdc_display and enable an SDC mapping on any field formatter.
Run Config Inspector (or drush config:inspect) against the relevant entity view display.
Observe missing schema rows for ...content..third_party_settings.sdc_display.

Proposed resolution

Add to config/schema/sdc_display.schema.yml:

field.formatter.third_party.sdc_display:
  type: sdc_display.third_party_settings

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A