Change to minimal Webpack output

[jryans]

This changes Webpack to only output errors, warnings, or new compilations.
This has the effect of hiding the massive list of modules. The giant list was
actually hiding warnings because they appear first and scroll off the
terminal.

[jryans]

The output now looks like:

<...compile progress as before...>
2020-01-24 22:30:32.843 [riot-js] <s> [webpack.Progress] 95% emitting
2020-01-24 22:30:32.843 [riot-js] <s> [webpack.Progress] 95% emitting HtmlWebpackPlugin
2020-01-24 22:30:32.999 [riot-js] <s> [webpack.Progress] 95% emitting HtmlWebpackPlugin
2020-01-24 22:30:33.294 [riot-js] <s> [webpack.Progress] 98% after emitting
2020-01-24 22:30:33.294 [riot-js] <s> [webpack.Progress] 100%
2020-01-24 22:30:33.294 [riot-js]
2020-01-24 22:30:33.359 [riot-js] ℹ ｢wdm｣:    2087 modules
2020-01-24 22:30:33.359 [riot-js] ℹ ｢wdm｣: Compiled successfully.