I18nize custom links in okta-signin-widget

Hello I am trying to add a custom link on okta-sigin-widget. It works, but I am unable to use i18n text.
Here is my sample code and highlighted code is where I am stuck. am I doing it right?

signInWidgetConfig = {
  language: 'en',                       // Try: [fr, de, es, ja, zh-CN] Full list: https://github.com/okta/okta-signin-widget#language-and-text
  i18n: {
    //Overrides default text when using English. Override other languages by adding additional sections.
    'en': {
      'custom.key': 'Testing',
      'primaryauth.title': 'Sign In',   // Changes the sign in text
      'primaryauth.submit': 'Sign In',  // Changes the sign in button
    }
  },
  // Changes to widget functionality
  features: {
    registration: true,                 // Enable self-service registration flow
    rememberMe: true,                   // Setting to false will remove the checkbox to save username
    //multiOptionalFactorEnroll: true,  // Allow users to enroll in multiple optional factors before finishing the authentication flow.
    //selfServiceUnlock: true,          // Will enable unlock in addition to forgotten password
    //smsRecovery: true,                // Enable SMS-based account recovery
    //callRecovery: true,               // Enable voice call-based account recovery
    router: true,                       // Leave this set to true for the API demo
  },
  baseUrl: 'https://live-widget.oktapreview.com',
  clientId: '0oaexo9c530ZUVuOj0h7',
  redirectUri: 'https://developer.okta.com/live-widget',
helpLinks: {
  custom: [
    {
      text: { 
        "i18n": {
        	"key": 'custom.key'
        }
     },
      href: 'https://acme.com/what-is-okta'
    }
  ]
}
};

signInWidget = new OktaSignIn(signInWidgetConfig);

function widgetSuccessCallback(res) {
  var key = '';
  if (res[0]) {
    key = Object.keys(res[0])[0];
    signInWidget.tokenManager.add(key, res[0]);
  }
  if (res[1]) {
    key = Object.keys(res[1])[0];
    signInWidget.tokenManager.add(key, res[1]);
  }
  if (res.status === 'SUCCESS') {
    var token = signInWidget.tokenManager.get(key);
    console.log("Logged in to Okta and issued token:");
    console.log(token);
    console.log("Reload this page to start over.");
    alert("Logged in! Check your developer console for details");
  }
}

function widgetErrorCallback (err) {
}

signInWidget.renderEl({el: '#widget-container'}, widgetSuccessCallback, widgetErrorCallback);