Fix negative content patterns

[bradlc]

This PR implements a fix for negative content patterns, e.g.

module.exports = {
  content: [
    './src/**/*.html',
    '!./src/ignore-me.html',
  ],
}

This is achieved by removing the path.resolve call. This would turn an input like !file into /Users/me/project/!file which is incorrect.

For context, path.resolve was originally used to work around a bug in fast-glob which has since been resolved.

Additionally, negative patterns are skipped when registering PostCSS dependencies.