Update doc

Signed-off-by: zitingguo-ms <[email protected]>

Author: Gfrom2016

src/sonic-yang-models/doc/Configuration.md

@@ -12,6 +12,7 @@ Table of Contents
    * [<strong>Redis and Json Schema</strong>](#redis-and-json-schema)
 
          * [ACL and Mirroring](#acl-and-mirroring)
+         * [BGP BBR](#bgp-bbr)
          * [BGP Device Global](#bgp-device-global)
          * [BGP Sessions](#bgp-sessions)
          * [BUFFER_PG](#buffer_pg)
@@ -369,6 +370,18 @@ and migration plan
     }
 }
 ```
+### BGP BBR
+
+The **BGP_BBR** table contains device-level BBR state.
+```
+{
+        "BGP_BBR": {
+            "all": {
+                "status": "enabled"/"disabled"
+            }
+        }
+}
+```
 ### BGP Device Global
 
 The **BGP_DEVICE_GLOBAL** table contains device-level BGP global state.