add rollup postcss plugin and import style from rrweb

rollup.config.js

@@ -2,6 +2,7 @@ import svelte from 'rollup-plugin-svelte';
 import resolve from 'rollup-plugin-node-resolve';
 import commonjs from 'rollup-plugin-commonjs';
 import { terser } from 'rollup-plugin-terser';
+import postcss from 'rollup-plugin-postcss';
 import pkg from './package.json';
 
 const production = !process.env.ROLLUP_WATCH;
@@ -38,6 +39,8 @@ export default [
     resolve(),
     commonjs(),
 
+    postcss(),
+
     // If we're building for production (npm run build
     // instead of npm run dev), minify
     production && terser(),