remove postcss comments

[timsuchanek]

When using plugins like postcss-next, postcss-inherit it occurs to me, that the sourcemap is added, even in production builds.
This removes the comments completely.
It reduced our build size from 9.8M to 5.2M

[giuseppeg]

Maybe we should make this behavior configurable.
We could pass postcss options to the processor from the babel plugin https://github.com/giuseppeg/styled-jsx-postcss/blob/master/src/babel.js#L91
https://babeljs.io/docs/plugins/#plugin-preset-options

[comerc]

My .postcssrc.js

module.exports = context => ({
  plugins: {
    'postcss-discard-comments': { removeAll: true },
    'postcss-inline-comment': {},
    'postcss-cssnext': {},
  },
})