Update dependency gulp to v5

Author: renovate[bot]

docs/themes/purehugo/package.json

@@ -1,6 +1,6 @@
 {
   "devDependencies": {
-    "gulp": "^3.8.11",
+    "gulp": "^5.0.0",
     "gulp-concat": "^2.5.2",
     "gulp-minify-css": "^1.1.0",
     "gulp-uglify": "^1.2.0"