refactor(@vant/cli): migrate to ESM package

packages/vant-cli/cjs/postcss.config.cjs

@@ -0,0 +1,42 @@
+const { join } = require('path');
+const { existsSync } = require('fs');
+const { ROOT } = require('./shared.cjs');
+
+function getRootPostcssConfig() {
+  const ROOT_POSTCSS_CONFIG_FILE = join(ROOT, 'postcss.config.js');
+  if (existsSync(ROOT_POSTCSS_CONFIG_FILE)) {
+    return require(ROOT_POSTCSS_CONFIG_FILE);
+  }
+  return { plugins: [] };
+}
+
+function getPostcssPlugins(rootConfig) {
+  const plugins = rootConfig.plugins || [];
+
+  if (Array.isArray(plugins)) {
+    const hasPostcssPlugin = plugins.find(
+      (plugin) =>
+        plugin === 'autoprefixer' && plugin.postcssPlugin === 'autoprefixer'
+    );
+    if (hasPostcssPlugin) {
+      return plugins;
+    }
+
+    return [require('autoprefixer'), ...plugins];
+  }
+
+  return {
+    autoprefixer: {},
+    ...plugins,
+  };
+}
+
+function resolvePostcssConfig() {
+  const rootConfig = getRootPostcssConfig();
+  return {
+    ...rootConfig,
+    plugins: getPostcssPlugins(rootConfig),
+  };
+}
+
+module.exports = resolvePostcssConfig();