docs: add a GH Actions badge [skip ci]

Author: AndreyBelym

README.md

@@ -6,8 +6,7 @@
 <p align="center">
 <i>Advanced JavaScript objects serialization</i>
 </p>
-<p align="center">
-  <a href="https://travis-ci.org/inikulin/replicator"><img alt="Build Status" src="https://api.travis-ci.org/inikulin/replicator.svg"></a>
+  <a href="https://github.com/inikulin/replicator/commits/master"><img alt="GitHub branch checks state" src="https://img.shields.io/github/checks-status/inikulin/replicator/master?label=tests"></a>
   <a href="https://www.npmjs.com/package/replicator"><img alt="NPM Version" src="https://img.shields.io/npm/v/replicator.svg"></a>
 </p>