Update build badge in README

Signed-off-by: Matthew Peveler <[email protected]>

Author: MasterOdin

README.md

@@ -1,4 +1,5 @@
-[![Build Status](https://travis-ci.org/grpc/grpc-node.svg?branch=master)](https://travis-ci.org/grpc/grpc-node)
+[![grpc-tools Build](https://github.com/grpc/grpc-node/actions/workflows/grpc-tools-build.yml/badge.svg)](https://github.com/grpc/grpc-node/actions/workflows/grpc-tools-build.yml)
+
 # gRPC on Node.js
 
 ## Implementations