Add OTA documentation

Closes: sysota#14 (closed)

index.rst

@@ -66,6 +66,12 @@ daily life.
    oniro/hardware-support/index
    building-project-documentation
 
+.. toctree::
+   :caption: OS Features
+   :maxdepth: 2
+
+   ota
+
 .. toctree::
    :caption: Supported Technologies
    :maxdepth: 2