Correct a comment mistype in webpack production config (#855)

packages/react-scripts/config/webpack.config.prod.js

@@ -42,7 +42,7 @@ var homepagePathname = homepagePath ? url.parse(homepagePath).pathname : '/';
 var publicPath = ensureSlash(homepagePathname, true);
 // `publicUrl` is just like `publicPath`, but we will provide it to our app
 // as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
-// Omit trailing shlash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
+// Omit trailing slash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
 var publicUrl = ensureSlash(homepagePathname, false);
 // Get environment variables to inject into our app.
 var env = getClientEnvironment(publicUrl);