build(deps): update dependency cssnano to v6

Author: renovate[bot]

package.json

@@ -18,7 +18,7 @@
     "@types/clipboard": "2.0.1",
     "@typescript-eslint/eslint-plugin": "5.62.0",
     "@typescript-eslint/parser": "5.62.0",
-    "cssnano": "4.1.11",
+    "cssnano": "6.0.1",
     "eslint": "8.45.0",
     "eslint-config-prettier": "8.8.0",
     "eslint-plugin-prettier": "4.2.1",