improve Babel and webpack configurations --> reduce JS bundle size

[tinovyatkin]

This PR contains several important changes regarding current build tooling, that coupled together, and allowed to decrease resulting JS bundle size to 19.35 Kb from current 22.11 Kb 🎉

Details below:

1. Babel: Removing dependency on separated plugins, included in preset-env and updating the rest to the latest versions. This required fixes in wrapped-element and wrapped-input classes, related to property definition (getter and setter must be defined/inherited in the same time).

2. webpack: you are using two, mostly identical configs - webpack.config.dev and webpack.config.prod. To avoid code duplication and taking advantage that we already have deepmerge dependency, I've separated common part of configs into webpack.config.common and reuse it. For production version you were using plugin to build minified and non-minified version, I've removed that in favor of documented way - returning array of configs. Also added libraryExport: 'default' here that allowed to use normal export default Choices in choices.js (the VSCode Typescript notice regarding lack of default export in this file was my major motivation for this whole refactoring). Upgraded all touched dependencies here to the latest versions.

3. Cypress: added jsconfig.json file to teach VSCode do IntelliSence for Cypress in spec files and stealed one fix for failing test from your earlier attempt ;-)

4. Upgraded redux and deepmerge to current versions chasing bundle size minimising

While I don't see how anything here may be a breaking change, I would suggest to release as minor version just in case (mostly due to Choices default export fix)

BONUS: Fixed lint.yml action to run ESLint only on affected src/scripts/**/*.js

[tinovyatkin]

@jshjohnson Looks good?

[jshjohnson]

Thanks! 🎉