Modernising for 2021

[eKoopmans]

Hi @sterzhakov , thanks for sharing karma-webpack-preprocessor. I would like to add some changes to the library to support my use cases - would you be open to a PR? Namely, I would like to add:

• support for newer versions of Webpack (by changing it to a peerDependency)
• allowing configuration options to be specified directly in webpackPreprocessor, and making the configPath optional
• support for the Karma customPreprocessors technique, to easily allow multiple configurations of the preprocessor in a single Karma setup
• support for Webpack watch behaviour

I'm happy to make these changes and submit them as a PR - I have already begun the work for my own use. Let me know if you're open. All the changes I've described should be backwards-compatible, though I'm focusing on Webpack 5, so we may need some additional testing if we want to ensure older versions (e.g. Webpack 2) stay supported.

[sterzhakov]

Hi @eKoopmans good thoughts, welcome ;)