buildscripts: initial kokoro config for auto releasing artifacts (#4391)

The script does nothing at the moment other than set up the kokoro
job.
diff --git a/buildscripts/kokoro/release_artifacts.cfg b/buildscripts/kokoro/release_artifacts.cfg
new file mode 100644
index 0000000..e2e8313
--- /dev/null
+++ b/buildscripts/kokoro/release_artifacts.cfg
@@ -0,0 +1,11 @@
+# Config file for internal CI
+
+# Location of the continuous shell script in repository.
+build_file: "grpc-java/buildscripts/kokoro/release_artifacts.sh"
+timeout_mins: 60
+
+action {
+  define_artifacts {
+    regex: ["**/mvn-artifacts/**"]
+  }
+}