Get rid of the Bower package manager

[tanius]

The current installation instructions in README.md instruct to install both bower and npm. That's a redundancy in the build environment that can be simplified by just using npm. If some packages are only available via bower, then we'd have to convert them to npm packages ourselves.

It just does not seem that Bower adds any major feature over NPM that would justify its use, much less using it in parallel with NPM for a small software like this.

Moreover, when installing Bower (sudo npm install -g bower), it even tells that it is now deprecated:

WARN deprecated [email protected]: We don't recommend using Bower for new projects. 
Please consider Yarn and Webpack or Parcel. You can read how to migrate 
legacy project here: https://bower.io/blog/2017/how-to-migrate-away-from-bower/

So it seems it's time to modernize that part of the build environment …