Upgrade postcss to v8

package.json

@@ -14,15 +14,14 @@
     "nuxt": "^2.14.12"
   },
   "devDependencies": {
-    "@nuxtjs/tailwindcss": "^3.4.2",
-    "@tailwindcss/postcss7-compat": "^2.0.3",
-    "autoprefixer": "^9",
+    "@nuxtjs/tailwindcss": "^4.1.2",
+    "autoprefixer": "^10.2.6",
     "highlight.js": "^10.6.0",
     "husky": "^5.0.9",
     "lint-staged": "^10.5.4",
-    "postcss": "^7",
+    "postcss": "^8.3.0",
     "prettier": "^2.2.1",
-    "tailwindcss": "npm:@tailwindcss/postcss7-compat",
+    "tailwindcss": "^2.1.2",
     "vue-backtotop": "^1.6.1",
     "vue-clipboard2": "^0.3.1"
   },