[Bug]: Configuration file is incorrectly imported from cli

[giggio]

Describe the bug

When using the cli and specifing the --config flag the file is incorrectly imported using await import, which creates an object with this structure:

{
  default: {}, // config
  'module.exports': {} // same config again
}

This is later merged with the other options, but the options never take effect.

This happens if you use the module.exports = {} syntax, which is explained in the docs.

This will work if you use an es module syntax, like so:

export const content = [];
export function defaultExtractor(content) { }
export const safelist = { };

But you will then get a warning from Node.js:

(node:2234469) [MODULE_TYPELESS_PACKAGE_JSON] Warning: Module type of file:///.../purgecss.config.js is not specified and it doesn't parse as CommonJS.
Reparsing as ES module because module syntax was detected. This incurs a performance overhead.

To Reproduce

1. Create a config file as per docs.
2. Create any css file named site.css.
3. Edit node_modules/purgecss/bin/purgecss.js to log the output of the config:

           options.skippedContentGlobs = skippedContentGlobs;
       if (output)
           options.output = output;
   +   console.log('***', options);
       return options;

4. Run: purgecss --config ./purgecss.config.js --css site.css --rejected

Expected Behavior

Configuration from cli args are merged into config from file and config file is not ignored.

Environment

Ubuntu 24, Node 23.10.0, Npm 10.9.2
@fullhuman/postcss-purgecss@7.0.2
purgecss@7.0.2

Add any other context about the problem here

This does not seem to be a docs only issue, as a warning is emitted by Node.js.

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