Added docs for open source Navigation Plugin

Summary:
Added docs for the Navigation Plugin.

I've added instructions on how to use the plugin with vanilla Android, or how to integrate it with a third party solution.

Reviewed By: danielbuechele

Differential Revision: D16856614

fbshipit-source-id: e99cb94318820bd926f50bd4ba205fb11396a9d8

docs/setup/navigation-plugin.md

@@ -0,0 +1,76 @@
+---
+id: navigation-plugin
+title: Navigation Plugin Setup
+sidebar_label: Navigation
+---
+
+## Android
+
+First, add the plugin to your Flipper client instance:
+```java
+import com.facebook.flipper.android.AndroidFlipperClient;
+import com.facebook.flipper.plugins.navigation.NavigationFlipperPlugin;
+
+final FlipperClient client = AndroidFlipperClient.getInstance(this);
+client.addPlugin(NavigationFlipperPlugin.getInstance());
+```
+
+Navigation events in the app can then be recorded by calling `sendNavigationEvent` method of the `NavigationFlipperPlugin` instance from anywhere in the app. This allows for the Navigation Plugin to be integrated into existing navigation frameworks.
+
+### Using Android Deep Links
+
+The Navigation Plugin can be used with built in [deep links for Android](https://developer.android.com/training/app-links/deep-linking).
+
+To deep link to an activity, edit the AndroidManifest.xml and add the intent filter for the given activity.
+
+```xml
+<intent-filter>
+  <action android:name="android.intent.action.VIEW" />
+  <category android:name="android.intent.category.DEFAULT" />
+  <category android:name="android.intent.category.BROWSABLE" />
+  <data android:scheme="flipper" android:host="deep_link_activity" />
+</intent-filter>
+```
+
+This will allow the user to jump to `flipper://deep_link_activity` within Flipper.
+
+To log that navigation event in  flipper, we can send the navigation event in the Activity's `onCreate` method.
+
+```java
+public class DeepLinkActivity extends AppCompatActivity {
+  @Override
+  protected void onCreate(final Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    NavigationFlipperPlugin.getInstance().sendNavigationEvent("flipper://deep_link_activity/");
+    ...
+```
+
+### Third Party Solutions
+The Navigation Plugin can easily be integrated into a third party navigation framework.
+
+#### AirBnB Deep Link Dispatch
+[Deep Link Dispatch](https://github.com/airbnb/DeepLinkDispatch) will work out of the box with Flipper for navigating to links, including support for url parameters. To add logging, simply add a BroadcastReceiver to your app that is called on any incoming deep links.
+
+```java
+public class DeepLinkReceiver extends BroadcastReceiver {
+  private static final String TAG = "DeepLinkReceiver";
+
+  @Override public void onReceive(Context context, Intent intent) {
+    String deepLinkUri = intent.getStringExtra(DeepLinkHandler.EXTRA_URI);
+    if (intent.getBooleanExtra(DeepLinkHandler.EXTRA_SUCCESSFUL, false)) {
+      NavigationFlipperPlugin.getInstance().sendNavigationEvent(deepLinkUri);
+    }
+  }
+}
+
+public class DeepLinkApplication extends Application {
+  @Override public void onCreate() {
+    super.onCreate();
+    IntentFilter intentFilter = new IntentFilter(DeepLinkHandler.ACTION);
+    LocalBroadcastManager.getInstance(this).registerReceiver(new DeepLinkReceiver(), intentFilter);
+  }
+}
+```
+
+## iOS
+iOS support is coming soon.