Fix some broken links

Summary:
KESHAmambo pointed out some internal links are broken on the website: https://twitter.com/KESHAmambo/status/1255443093542895619

The way relative links are processed in docusaurus v1 and v2 has changed. This fixes them up.

Reviewed By: mweststrate

Differential Revision: D21301293

fbshipit-source-id: 7610e38a55bc066625373cf2eee9a3efb63aec08

docs/features/crash-reporter-plugin.mdx

@@ -4,7 +4,7 @@ title: Crash Reporter
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Crash Reporter](setup/crash-reporter-plugin)
+→ [See setup instructions for the Crash Reporter](../setup/crash-reporter-plugin)
 
 
 The Crash Reporter Plugin shows a notification in Flipper whenever an app crashes. You can click on the notification to see crash information like stacktrace and other metadata. For Android, you can click the "Open in Logs" button to jump to the row in the Logs plugin with the crash information.

docs/features/databases-plugin.mdx

@@ -4,7 +4,7 @@ title: Databases
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Databases plugin](setup/databases-plugin)
+→ [See setup instructions for the Databases plugin](../setup/databases-plugin)
 
 The Databases plugin provides developers with read-write access to their databases:
 - browse your tables' data

docs/features/images-plugin.mdx

@@ -4,7 +4,7 @@ title: Images
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the images plugin](setup/images-plugin)
+→ [See setup instructions for the images plugin](../setup/images-plugin)
 
 The images plugin allows you to inspect what images were fetched, where they are
 coming from and selectively clear caches. Currently, the plugin supports

docs/features/layout-plugin.mdx

@@ -4,7 +4,7 @@ title: Layout Inspector
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Layout Inspector](setup/layout-plugin)
+→ [See setup instructions for the Layout Inspector](../setup/layout-plugin)
 
 The Layout Inspector in Flipper is useful for a ton of different debugging scenarios. First of all, you can inspect what views the hierarchy is made up of as well as what properties each view has. This is incredibly useful when debugging issues with your product.
 

docs/features/leak-canary-plugin.mdx

@@ -3,7 +3,7 @@ id: leak-canary-plugin
 title: LeakCanary
 ---
 
-→ [See setup instructions for the LeakCanary](setup/leak-canary-plugin)
+→ [See setup instructions for the LeakCanary](../setup/leak-canary-plugin)
 
 The LeakCanary plugin provides developers with Flipper support for [LeakCanary](https://github.com/square/leakcanary), an open source memory leak detection library.
 

docs/features/navigation-plugin.mdx

@@ -4,7 +4,7 @@ title: Navigation
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Navigation Plugin](setup/navigation-plugin)
+→ [See setup instructions for the Navigation Plugin](../setup/navigation-plugin)
 
 The Navigation Plugin allows users to quickly navigate to deep links within their mobile applications to help speed up the development cycle. The plugin is designed to integrate easily within your existing navigation framework or as a stand alone tool. Users can bookmark deep links and jump to them via the button in the tool bar.
 

docs/features/network-plugin.mdx

@@ -4,7 +4,7 @@ title: Network
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Network plugin](setup/network-plugin)
+→ [See setup instructions for the Network plugin](../setup/network-plugin)
 
 Use the Network inspector to inspect outgoing network traffic in your apps. You can easily browse all requests being made and their responses. The plugin also supports gzipped responses.
 

docs/features/sandbox-plugin.mdx

@@ -3,6 +3,6 @@ id: sandbox-plugin
 title: Sandbox
 ---
 
-→ [See setup instructions for the Sandbox plugin](setup/sandbox-plugin)
+→ [See setup instructions for the Sandbox plugin](../setup/sandbox-plugin)
 
 The sandbox plugin allows developers to test changes in their apps by pointing them to a sandbox environment. It provides a simple UI to set and modify the URL to a development host that acts as a sandbox directly on the desktop, which prevents you from entering potentially long and complicated URL inside your app. 

docs/features/shared-preferences-plugin.mdx

@@ -4,7 +4,7 @@ title: Shared Preferences
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
 
-→ [See setup instructions for the Shared Preferences plugin](setup/shared-preferences-plugin)
+→ [See setup instructions for the Shared Preferences plugin](../setup/shared-preferences-plugin)
 
 Easily inspect and modify the data contained within your app's shared preferences.