Add DB client proto repo.

Author: wu-sheng

data/docs.yml

@@ -331,6 +331,14 @@
         - version: v0.9.0
           link: /docs/skywalking-banyandb/v0.9.0/readme/
           commitId: 0154f620472f5cf9412db45b28e35ee910c4d39d
+    - name: BanyanDB Client Proto
+      icon: banyan-db
+      description: Protocol definitions in Protobuf/gRPC for BanyanDB clients
+      user: apache
+      repo: skywalking-banyandb-client-proto
+      docs:
+        - version: Next
+          link: https://github.com/apache/skywalking-banyandb-client-proto/blob/main/README.md
     - name: BanyanDB Java Client
       icon: banyan-db
       description: The client implementation for SkyWalking BanyanDB in Java