Update Docusaurus metadata (#3881)

* Update Docusaurus to alpha.64

* Fix validation issues and swap Twitter card config

* Fix broken Immutable FAQ link

Author: markerikson

docs/recipes/UsingImmutableJS.md

@@ -246,7 +246,7 @@ Smart components that access the store via React Redux’s `connect` function mu
 **Documentation**
 
 - [Recipes: Computing Derived Data](./ComputingDerivedData.md)
-- [FAQ: Immutable Data](/faq/ImmutableData.html#immutability-issues-with-react-redux)
+- [FAQ: Immutable Data](../faq/ImmutableData.md#immutability-issues-with-react-redux)
 - [Reselect Documentation: How do I use Reselect with Immutable.js?](https://github.com/reduxjs/reselect/#q-how-do-i-use-reselect-with-immutablejs)
 
 **Articles**

website/docusaurus.config.js

@@ -7,19 +7,21 @@ module.exports = {
   organizationName: 'reduxjs',
   projectName: 'redux',
   themeConfig: {
-    image: 'https://redux.js.org/img/redux-logo-landscape.png',
-    disableDarkMode: false,
+    image: 'img/redux-logo-landscape.png',
+    metadatas: [{ name: 'twitter:card', content: 'summary' }],
     prism: {
       theme: require('./src/js/monokaiTheme.js')
     },
+    colorMode: {
+      disableSwitch: false
+    },
     navbar: {
       title: 'Redux',
-      image: 'img/redux-logo-landscape.png',
       logo: {
         alt: 'Redux Logo',
         src: 'img/redux.svg'
       },
-      links: [
+      items: [
         {
           label: 'Getting Started',
           to: 'introduction/getting-started',