refactor(renderer.prod.js): adjust deps and webpack file for electron build

[ramfox]

• removed core-js@3.0.1 dependency
• removed core-js reference in .babelrc config
• upgraded deps to latest release
• removed ExtractTextPlugin from webpack.config.renderer.prod.js file

These changes allow us to build the minified electron app with no errors!

[ramfox]

When this is merged, it's a candidate for a new release!!