feat: upgrade to frontend-platform (#60)

BREAKING CHANGE: This package now relies upon frontend-platform instead of individual runway packages.

example/index.jsx

@@ -1,6 +1,6 @@
 import React from 'react';
 import { render } from 'react-dom';
-import { IntlProvider } from '@edx/frontend-i18n';
+import { IntlProvider } from '@edx/frontend-platform/i18n';
 
 import './index.scss';
 import Footer from '../src';
@@ -9,7 +9,7 @@ const App = () => (
   <div>
     <IntlProvider locale="en">
       <Footer
-        onLanguageSelected={(languageCode) => {}}
+        onLanguageSelected={() => {}}
         supportedLanguages={[
           { label: 'English', value: 'en' },
           { label: 'Español', value: 'es' },