Schema for export link formatter is missing

Problem/Motivation

I can see that we missed schema for this formatter.

Steps to reproduce

Use this formatter for link field and check config inspector module. You can see missing schema.

Proposed resolution

Add:

field.formatter.settings.link_export:
  type: field.formatter.settings.image
  mapping:
    export_text:
      type: boolean
      label: 'Export text attribute'

Remaining tasks

User interface changes

API changes

Data model changes