[Feature Request]: custom CSS transformer support

[ThatOneCalculator]

What problem does this feature solve?

Vite allows the use of a custom CSS transformer (only lightningcss as of right now), and having that functionality in Farm would be great.

What does the proposed API look like?

In farm.config.ts:

	css: {
		transformer: "lightningcss",
	},

[wre232114]

Farm is based on plugins, so all transformers should be implemented as a plugin, we won't support css.transformer, instead, we'll provide a plugin-lightningcss later

[ThatOneCalculator]

Could https://github.com/lawrencecchen/vite-plugin-lightningcss be used as a base?

[wre232114]

Yes, we'll provide a pure rust lightningcss plugin later(maybe this month, and PR welcome)