Add doc submodule for esr-server

Change-Id: I1fa581810e67900b921dd9d53940d8dc2a3d6194
Issue-ID: AAI-379
Signed-off-by: lizi00164331 <li.zi30@zte.com.cn>
diff --git a/.gitmodules b/.gitmodules
index 8eb97cd..35ee2bd 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -88,3 +88,6 @@
 	url = ../dmaap/messagerouter/messageservice
         branch = .
         ignore = dirty
+[submodule "docs/submodules/aai/esr-server.git"]
+	path = docs/submodules/aai/esr-server.git
+	url = ../aai/esr-server