Improve installation/update instructions

Summary:
The installation instructions didn't flow very well.

"Using flipper at Facebook" is now gone. It's installation steps have been moved into the desktop app page, with internal/external switching.

I've also removed the "Updating Flipper" internal page, and put equivalent info in the installation section.

Reviewed By: nikoant

Differential Revision: D25637831

fbshipit-source-id: 2af2abf57793d54804f5c45e3335b8641743e1c8

docs/getting-started/index.mdx

@@ -3,20 +3,36 @@ id: index
 title: Desktop App
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
+import {FbInternalOnly, OssOnly} from 'internaldocs-fb-helpers';
+
+import FbInstallation from './fb/installation.mdx';
 
 Flipper helps you debug Android and iOS apps running in an emulator/simulator or connected physical development devices. Flipper consists of two parts:
 
 - The desktop app
 - The native mobile SDKs for Android and iOS
 
-To use Flipper, you need to add the mobile SDK to your app. If you are using React Native 0.62 or higher, this is largely done automatically for you.
+Once you start Flipper and launch an emulator/simulator or connect a device, you'll start to see the device logs (and any other device-level plugins that work with your device).
 
----
+To see app specific data, you need to integrate the Flipper SDK into your app. See the relevant section in the sidebar for how to do that.
 
-The desktop part of Flipper doesn't need any particular setup. Simply download the latest build for [Mac](https://www.facebook.com/fbflipper/public/mac), [Linux](https://www.facebook.com/fbflipper/public/linux) or [Windows](https://www.facebook.com/fbflipper/public/windows) and launch it. In order to work properly, Flipper requires a working installation of the Android and (if where applicable) iOS development tools on your system, as well as the [OpenSSL](https://www.openssl.org) binary on your `$PATH`.
+## Installation
+
+<OssOnly>
+
+The desktop part of Flipper doesn't need any particular setup. Simply download the latest build for [Mac](https://www.facebook.com/fbflipper/public/mac), [Linux](https://www.facebook.com/fbflipper/public/linux) or [Windows](https://www.facebook.com/fbflipper/public/windows) and launch it.
+
+In order to work properly, Flipper requires a working installation of the Android and (if where applicable) iOS development tools on your system, as well as the [OpenSSL](https://www.openssl.org) binary on your `$PATH`.
 
 A compatible OpenSSL for Windows can be downloaded [here](https://slproweb.com/products/Win32OpenSSL.html) or from Chocolatey with `choco install openssl`.
 
-Once you start Flipper and launch an emulator/simulator or connect a device, you will already be able to see the device logs in Flipper. To see app specific data, you need to integrate our native SDKs with your app.
+</OssOnly>
+<FbInternalOnly>
 
-<img alt="Logs plugin" src={useBaseUrl("img/initial.png")} />
+<FbInstallation />
+
+</FbInternalOnly>
+
+## Troubleshooting
+
+If you run into problems, check out the [troubleshooting page](../troubleshooting.mdx), and failing that, check <OssOnly>[GitHub Issues](https://github.com/facebook/flipper/issues).</OssOnly><FbInternalOnly>the [workplace group](https://fb.workplace.com/groups/230455004101832/).</FbInternalOnly>

website/sidebars.js

@@ -37,7 +37,6 @@ module.exports = {
   },
   setup: {
     'Getting Started': [
-      ...fbInternalOnly(['getting-started/fb/using-flipper-at-facebook']),
       'getting-started/index',
       ...fbInternalOnly(['fb/Add-flipper-to-android-app']),
       'getting-started/android-native',
@@ -85,9 +84,7 @@ module.exports = {
       'extending/desktop-plugin-structure',
       'extending/testing',
       'extending/debugging',
-      ...fbInternalOnly([
-        'fb/adding-analytics-0',
-      ]),
+      ...fbInternalOnly(['fb/adding-analytics-0']),
       'extending/plugin-distribution',
     ],
     'Desktop plugin APIs': [
@@ -98,7 +95,7 @@ module.exports = {
       ...fbInternalOnly([
         {
           'QPL linting': ['fb/building-a-linter', 'fb/active-linters'],
-        }
+        },
       ]),
       {
         'Deprecated APIs': [
@@ -127,7 +124,6 @@ module.exports = {
         'fb/Flipper-fbsource-Pinning',
         'fb/Flipper-Release-Cycle',
         'fb/Add-Support-Group-to-Flipper-Support-Form',
-        'fb/Help-Updating-Flipper',
         'fb/Alerts',
         'fb/bundling',
         'fb/Certificate-Exchange-Diagram',