Upgraded Webpack to solve the issues with deprecated versions

[aldomonteiro]

This PR is to solve the issues related to webpack configuration. I upgraded the webpack-dev-server to the latest version and fixed the webpack.config.js, addressing the open issue of the app.

I am using Yarn on my computer, so, I am sending the yarn.lock file in the PR. However, I did not update the README to use it, because it is possible to run smoothly this app using npm, I guess.