Add doc reference for Multi VIM/Cloud project

This patch is to add doc reference for Multi VIM/Cloud project.

Change-Id: I42dc8878912ae6c9ac52b890d7fc914b80e54881
issue-id: MULTICLOUD-86
Signed-off-by: xinhuili <lxinhui@vmware.com>
diff --git a/.gitmodules b/.gitmodules
index b13e520..ee9b415 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -153,3 +153,6 @@
 	url = ../integration
 	branch = .
 	ignore = dirty
+[submodule "docs/submodules/multicloud/framework.git"]
+	path = docs/submodules/multicloud/framework.git
+	url = ../multicloud/framework