bumped deps; replaced gulp-concat-util

gulpfile.js

@@ -2,7 +2,7 @@ const _gulp = require('gulp');
 const _sass = require('gulp-sass');
 const _prettyError = require('gulp-prettyerror');
 const _cleanCSS = require('gulp-clean-css');
-const _concat = require('gulp-concat-util');
+const _concat = require('gulp-concat');
 
 _gulp.task('sass', function (){
     return _gulp.src('./assets/layout.scss')

package.json

@@ -42,13 +42,13 @@
     "repository": "AndiDittrich/HttpErrorPages",
     "license": "MIT",
     "devDependencies": {
-        "commander": "^5.1.0",
+        "commander": "^6.2.0",
         "eslint": "^7.4.0",
         "eslint-config-aenondynamics": "^0.2.0",
         "express": "^4.17.1",
         "gulp": "^4.0.2",
         "gulp-clean-css": "^4.3.0",
-        "gulp-concat-util": "^0.5.5",
+        "gulp-concat": "^2.6.1",
         "gulp-prettyerror": "^2.0.0",
         "gulp-sass": "^4.1.0",
         "koa": "^2.13.0",