Evaluate esModule options in webpack loaders

Created by: ianschmitz

css-loader and style-loader now support a esModule option to emit to ESM instead of CJS, which can improve tree shaking/module concatenation in webpack, but I haven't had a chance to see if it's compatible with our other CSS loaders.

file-loader and url-loader now enable esModule by default, but have dropped support for node < 10.13.0.

Let's see if there's any benefit to enabling these in our webpack config.