Fixed TypeScript related no-unused-vars linting errors

no issue

- Function types in TypeScript can have what looks like an unused variable for the eslint. It's part of the TypeScript language and should be fully supported out of the box.

ghost/model-to-domain-event-interceptor/.eslintrc.js

@@ -1,7 +1,11 @@
 module.exports = {
     parser: '@typescript-eslint/parser',
-    plugins: ['ghost'],
+    plugins: ['ghost', '@typescript-eslint'],
     extends: [
         'plugin:ghost/node'
-    ]
+    ],
+    rules: {
+        'no-unused-vars': 'off',
+        '@typescript-eslint/no-unused-vars': ['error']
+    }
 };