feat: enhance CSS processing and content rendering

- Added postcss-nesting for improved CSS nesting support
- Updated dependencies to support new CSS processing features
- Modified HTML content handling to improve accessibility and styling
- Enhanced post content parsing for better rendering and SEO

package.json

@@ -37,6 +37,7 @@
     "eslint-plugin-astro": "^1.2.3",
     "eslint-plugin-format": "^0.1.2",
     "lint-staged": "^15.2.8",
+    "postcss-nesting": "^13.0.0",
     "prettier-plugin-astro": "^0.14.1",
     "simple-git-hooks": "^2.11.1",
     "std-env": "^3.7.0"