[FAB-9336] Update Docs readme

Updated Docs README for local build

Change-Id: I65505065327715ebfced3ea8aba71e546be08c0f
Signed-off-by: pama-ibm <pama@ibm.com>

Author: pamandrejko

docs/README.md

@@ -68,6 +68,7 @@ directory. Note: you may need to adjust depending on your OS.
 ```
 sudo pip install Sphinx
 sudo pip install sphinx_rtd_theme
+sudo pip install recommonmark==0.4.0
 cd fabric/docs # Be in this directory. Makefile sits there.
 make html
 ```