[VOL-3960] Adding VOLTHA 2.7 release notes alongside PM counters update and ONU SW update.

Change-Id: I37a99f566b63c7315458fce152481ff471a78879
diff --git a/index.rst b/index.rst
index b8d8d75..b4bce27 100644
--- a/index.rst
+++ b/index.rst
@@ -77,6 +77,14 @@
 .. toctree::
    :maxdepth: 1
    :hidden:
+   :caption: Operations
+
+   ONU software update <voltha-openonu-adapter-go/ONU_Upgrade_Notes.md>
+   ONU Performance Metrics <voltha-openonu-adapter-go/PM_Notes.md>
+
+.. toctree::
+   :maxdepth: 1
+   :hidden:
    :caption: Testing
 
    VOLTHA system tests <voltha-system-tests/README.md>