[v4] Allow Lightning CSS options through optimize key

[cossssmin]

Would be super useful if we could pass Lightning CSS options to the PostCSS plugin.

Looking at the types and source, looks like we can only toggle minification:

type PluginOptions = {
    base?: string;
    optimize?: boolean | {
        minify?: boolean;
    };
};

Would be useful if we could define targets or include/exclude for example 👍

[cossssmin]

Bumping this 🙈

So in Maizzle for example, in order to lower down the CSS syntax to be used for HTML emails, I need to be able to tell Lightning to use a certain target, like this:

tailwindcss({
  optimize: {
    minify: false,
    targets: {
      ie: 1,
    },
  },
})

Basically make optimize accept a Lightning config object.

Right now I'm running Lightning twice, the second time after Tailwind, just to have it run with a custom config to lower down the CSS syntax.

I think this would be useful to all implementations, not just the PostCSS one. And not just for Maizzle, but other frameworks like React Email, which currently cannot support responsive utilities because the ones Tailwind generates use nested @media queries, which have very poor support in email clients.