Missing arrow syntax in README.md

[masautt]

The first code block in the README is missing the arrow syntax for the callback function for app.on("ready").

Current README codeblock

app.on('ready', () {
  let mainWindow = new BrowserWindow({width: 800, height: 600});

  mainWindow.loadUrl(`file://${__dirname}/index.html`);
  // the rest...
});

FixedREADME codeblock

app.on('ready', ( ) => {
  let mainWindow = new BrowserWindow({width: 800, height: 600});

  mainWindow.loadUrl(`file://${__dirname}/index.html`);
  // the rest...
});