Add autoprefixer and postcss as dev deps

NPM installs auto-install peer deps now but yarn does not. We need to explicitly add them to the dev dependencies.

Author: thecrypticace

package.json

@@ -23,8 +23,10 @@
     "tailwindcss": ">=3.0.0 || >= 3.0.0-alpha.1"
   },
   "devDependencies": {
+    "autoprefixer": "^10.4.2",
     "concurrently": "^5.3.0",
     "live-server": "^1.2.1",
+    "postcss": "^8.4.5",
     "tailwindcss": "^3.0.2"
   },
   "dependencies": {