Batch processing?

We're using purgecss in our postcss configuration. Our purgecss takes a ~3 seconds to run. This plugin will run that 3 second task on each individual file. I think it would make more sense to concatenate all the css files to a single ast and then process that with postcss. My tests show that it would take 3 seconds for ALL the files instead of _per_ file.

Start by tracing how the PostCSS configuration invokes PurgeCSS for each CSS file. Confirm whether the files can be combined into one AST and processed once, then verify that the generated CSS remains correct and that the work runs once for the full batch rather than once per file.

Written by the indexing model from the issue text.