Spelling

src/App.js

@@ -30,7 +30,7 @@ class App extends IPCContainer {
   componentDidMount() {
     const detectUpgrades = () => {
       if (this.props.AppPlatform === 'unknown') {
-        this.props.notifyError('Operation system is not supported.', true);
+        this.props.notifyError('Operating system is not supported.', true);
       } else {
         this.props.loadReleases();
       }