app/node_modules/@ionic/angular/schematics/collection.json

{
  "$schema": "../../node_modules/@angular-devkit/schematics/collection-schema.json",
  "schematics": {
  "ng-add": {
      "description": "Add Ionic to your project",
      "factory": "./add",
      "schema": "./add/schema.json"
    }
  }
}