TSLint plugin

Normally, when using `transpileOnly` + `ForkTsCheckerWebpackPlugin`, you want to do linting in the `ForkTsCheckerWebpackPlugin` (which it supports by supplying a config object `{ tslint: ''}`). It's a one-liner.

Sadly, the current solution with hardcoded 'smart' webpack config merging does not allow you to replace (or remove) a plugin entry in the webpack config, so there's currently no way to add this support by yourself without losing CLI support :( (https://github.com/electron-userland/electron-webpack/issues/11, https://github.com/electron-userland/electron-webpack/issues/33, https://github.com/electron-userland/electron-webpack/issues/92). So, in lieu of a proper solution for more powerful config transformations, could TSLint be added as a plugin?