Rename FB Internal to Under the Hood

Summary:
I think there's a need for an "implementation details" section of the site. Especially as we're moving the rest of our wiki content there.

I see it as a good thing, because now we have a place for implementation details relevant to OSS contributors too, it's not all fb-specific.

Reviewed By: nikoant

Differential Revision: D25614909

fbshipit-source-id: 5ec081e6450a9ad1c30785ae4cca74b6fa0d2630

docs/internals/index.mdx

@@ -0,0 +1,8 @@
+---
+id: index
+title: Internals
+sidebar_label: Internals
+---
+
+This part of the site is for those interested in **how** Flipper works, to help those wanting to modify the source code of the application itself.
+

website/docusaurus.config.js

@@ -56,15 +56,11 @@ const siteConfig = {
           label: 'GitHub',
           position: 'right',
         },
-        // start-internal-navbar-example
-        ...fbInternalOnly([
         {
-            to: 'docs/fb/index',
+          to: 'docs/internals/index',
-            label: 'FB Internal',
+          label: 'Under the Hood',
           position: 'right',
         },
-        ]),
-        // end-internal-navbar-example
       ],
     },
     colorMode: {

website/sidebars.js

@@ -115,10 +115,12 @@ module.exports = {
       'extending/layout-inspector',
     ],   
   },
-  'fb-internal': {
+  internals: {
-    'FB Internal': fbInternalOnly([
+    Internals: [
-      'fb/index',
+      'internals/index',
       'extending/public-releases',
+      'extending/testing-rn',
+      ...fbInternalOnly([
         'fb/release-infra',
         'fb/LauncherConfig',
         'fb/hacking-on-launcher',
@@ -126,7 +128,6 @@ module.exports = {
         'fb/Flipper-Release-Cycle',
         'fb/Add-Support-Group-to-Flipper-Support-Form',
         'fb/Help-Updating-Flipper',
-      'extending/testing-rn',
         'fb/Alerts',
         'fb/bundling',
         'fb/Certificate-Exchange-Diagram',
@@ -137,5 +138,6 @@ module.exports = {
         'fb/sandcastle',
         'fb/Star-Ratings',
       ]),
+    ],
   },
 };