Documenting how to use pprof tool with examples

Change-Id: I24786439ead3b33bf65c6f5c077517de9ba853e1
diff --git a/index.rst b/index.rst
index 3432470..821b99d 100644
--- a/index.rst
+++ b/index.rst
@@ -167,6 +167,7 @@
 
    VOLTHA system tests <voltha-system-tests/README.md>
    testing/index.rst
+   testing/memory_usage_pprof.rst
 
 .. toctree::
    :maxdepth: 1