Move plugin docs to plugin folders

Summary: Moved plugin documentation and related assets to plugin folders, fixed links and configured redirects where required. Now these docs are used for both showing docs in Flipper and generating Flipper docs website.

Reviewed By: passy

Differential Revision: D29465567

fbshipit-source-id: 3ec4240b215b0d5baea5154f64266a9ba7ead3a5

desktop/plugins/public/crash_reporter/docs/overview.mdx

@@ -0,0 +1,7 @@
+import useBaseUrl from '@docusaurus/useBaseUrl';
+
+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.
+
+<img alt="UI" src={useBaseUrl("img/crashreporterplugin.png")} />
+
+<img alt="Notification" src={useBaseUrl("img/crashreporterpluginnotification.png")} />

desktop/plugins/public/crash_reporter/docs/setup.mdx

@@ -0,0 +1,20 @@
+import useBaseUrl from '@docusaurus/useBaseUrl';
+import Link from '@docusaurus/Link';
+
+You do not have to instantiate it in your app in order to use its basic functionality mentioned <Link to={useBaseUrl("/docs/features/plugins/crash-reporter")}>here</Link>. You can also use crash reporter plugin to send the notifications for the exception which you suppress in your Android application. You could even use it to send the notifications when the [Litho Error Boundary](https://fblitho.com/docs/error-boundaries) is triggered. In order to send your custom notification you will have to follow the following steps.
+
+## Android
+
+Instantiate and add the plugin in `FlipperClient`.
+```java
+import com.facebook.flipper.plugins.crashreporter.CrashReporterPlugin;
+
+client.addPlugin(CrashReporterPlugin.getInstance());
+```
+
+Use the following API to trigger your custom crash notification.
+
+```java
+import com.facebook.flipper.plugins.crashreporter.CrashReporterPlugin;
+CrashReporterPlugin.getInstance().sendExceptionMessage(Thread.currentThread(), error);
+```