[astro-purgecss] Allow passing options to customize PurgeCSS

[mhdcodes]

Description

We need to allow passing certain options to the plugin to be passed to the underneath PurgeCSS.

Ref

• https://purgecss.com/configuration.html

Example

import { defineConfig } from 'astro/config';
import purgecss from "astro-purgecss";

// https://astro.build/config
export default defineConfig({
  integrations: [purgecss({
    fontFace: true,
    keyframes: true,
    variables: true,
    safelist: ['random', 'yep', 'button', /^nav-/]
  })]
});