I have the following postcss.config.js file:

```
// postcss.config.js
module.exports = {
    plugins: [
        require('postcss-import'),
        require('tailwindcss'),
        require('autoprefixer'),
    ]
}

```

and the following tailwind.config.js file:

```

// tailwind.config.js
module.exports = {
    purge: [
        './src/cljs/foo/*.cljs',
        './target/cljs-runtime/*.js',
        './target/cljsbuild/public/js/*',
        './target/cljsbuild/public/js/cljs-runtime/*',
        './target/*'
    ],
    theme: {},
    variants: {},
    plugins: [],
}

```

And my goal is to compress the css generated, for which I've added the purge key in tailwind.config.js.

To generate the css from the .src tailwind file, styles.src.css:

```
@tailwind base;
@tailwind components;
@tailwind utilities;

```

I'm running the command:

```
postcss ./resources/public/css/styles.src.css -o ./resources/public/css/styles.css

```

from the root directory of my project that contains both the tailwind.config.js and the postcss.config.js. Yet after running the command, the generated css is 1.2MB, as big as what I had without the purge key. Why isn't postcss purge working?