chore: add PostCSS

package.json

@@ -34,6 +34,7 @@
     "@typescript-eslint/eslint-plugin": "6.7.4",
     "@typescript-eslint/parser": "6.7.4",
     "astro-eslint-parser": "0.16.0",
+    "autoprefixer": "10.4.16",
     "commitizen": "4.3.0",
     "cz-conventional-changelog": "3.3.0",
     "eslint": "8.50.0",
@@ -51,6 +52,7 @@
     "husky": "8.0.3",
     "lint-staged": "14.0.1",
     "postcss-html": "1.5.0",
+    "postcss-nesting": "12.0.1",
     "prettier": "3.0.3",
     "prettier-plugin-astro": "0.12.0",
     "standard-version": "9.5.0",