RDKEMW-6916: Create documentation for AppManager

Reason for change : Created md file for AppManager plugin
Test Procedure: NA
Risks: Low
Priority: P1
Signed-off-by: Pavithra V [email protected]

Author: pavithraviswa

docs/_sidebar.md

@@ -3,6 +3,7 @@
 - [**Overview**](overview/intro.md)
 - [**API Reference**](/README)
   - [Analytics](apis/AnalyticsPlugin.md)
+  - [AppManager](apis/AppManagerPlugin.md)
   - [AVInput](apis/AVInputPlugin.md)
   - [Bluetooth](apis/BluetoothPlugin.md)
   - [DeviceDiagnostics](apis/DeviceDiagnosticsPlugin.md)
@@ -37,6 +38,7 @@
   - [ResourceManager](apis/ResourceManagerPlugin.md)
   - [ScreenCapture](apis/ScreenCapturePlugin.md)
   - [SharedStorage](apis/SharedStoragePlugin.md)
+  - [StorageManager](apis/StorageManagerPlugin.md)
   - [SystemAudioPlayer](apis/SystemAudioPlayerPlugin.md)
   - [SystemMode](apis/SystemModePlugin.md)
   - [SystemServices](apis/SystemPlugin.md)