Add Sandy to internal documentation

Summary:
Scaffolded some internal Sandy notes and made them only internally available.

Since most of the pipeline was already set up by jknoxville, it is unclear to me if something needs to be done to set up the auto redirect from fbflipper.com

Reviewed By: jknoxville

Differential Revision: D22233534

fbshipit-source-id: 4bdf5535f5745e7e4d335647759c6cf1b7cc73c6

website/docusaurus.config.js

@@ -7,17 +7,22 @@
  * @format
  */
 
+function FBInternalWithOssFallback(elements, fallback) {
+  return process.env.FB_INTERNAL ? elements : fallback;
+}
+
 const repoUrl = 'https://github.com/facebook/flipper';
 
 const siteConfig = {
-  title: 'Flipper',
+  title: FBInternalWithOssFallback('Flipper @FB', 'Flipper'),
   tagline: 'Extensible mobile app debugging',
-  url: 'https://fbflipper.com/',
+  url: FBInternalWithOssFallback('https://flipper.thefacebook.com/', 'https://fbflipper.com/'),
   baseUrl: '/',
   projectName: 'flipper',
+  // TODO: T69061026 enable once sandy docs are complete: external_domain: 'fbflipper.com',
   themeConfig: {
     navbar: {
-      title: 'Flipper',
+      title: FBInternalWithOssFallback('Flipper @FB', 'Flipper'),
       logo: {
         alt: 'Flipper Logo',
         src: 'img/icon.png',
@@ -65,13 +70,13 @@ const siteConfig = {
         title: "I'm a dolphin not a whale!",
       },
     },
-    algolia: {
+    algolia: FBInternalWithOssFallback(undefined, {
       apiKey: '2df980e7ffc95c19552790f7cad32666',
       indexName: 'fbflipper',
       algoliaOptions: {
         hitsPerPage: 5,
       },
-    },
+    }),
     prism: {
       additionalLanguages: ['groovy', 'java', 'kotlin', 'ruby', 'swift'],
     },
@@ -93,7 +98,7 @@ const siteConfig = {
       {
         docs: {
           path: '../docs',
-          sidebarPath: require.resolve('./sidebars.json'),
+          sidebarPath: require.resolve('./sidebars.js'),
           editUrl: 'https://github.com/facebook/flipper/blob/master/website',
         },
         theme: {