[sonic-extension.yang]: Adding sonic-extension.yang (sonic-net#60)

Signed-off-by: Praveen Chaudhary pchaudhary@linkedin.com

src/sonic-yang-mgmt/yang-models/sonic-extension.yang

@@ -0,0 +1,27 @@
+module sonic-extension {
+
+    yang-version 1.1;
+
+    namespace "http://github.com/Azure/sonic-extension";
+    prefix sonic-extension;
+
+    organization "Linkedin Corporation";
+
+    contact "lnos_coders@linkedin.com";
+
+    description "Head yang Module for SONiC OS";
+
+    revision 2019-07-01 {
+        description "First Revision";
+    }
+
+    extension key-regex-configdb-to-yang {
+        description "Key regex used to convert config DB keys to YANG Config";
+        argument "value";
+    }
+
+    extension key-regex-yang-to-configdb {
+        description "Key regex used to convert config DB keys to YANG Config";
+        argument "value";
+    }
+}