samples: Add examples on adding tags to instances

Author: dohun-dev

samples/snippets/src/main/java/com/example/bigtable/InstanceAdminExample.java

@@ -107,7 +107,8 @@ public void createProdInstance() {
           CreateInstanceRequest.of(instanceId)
               .addCluster(clusterId, "us-central1-f", 3, StorageType.SSD)
               .setType(Instance.Type.PRODUCTION)
-              .addLabel("department", "accounting");
+              .addLabel("department", "accounting")
+              .addTag("tagKeys/12345", "tagValues/45678");
       // Creates a production instance with the given request.
       try {
         Instance instance = adminClient.createInstance(createInstanceRequest);