add gulp clean css to minify css

Gulpfile.js

@@ -1,13 +1,15 @@
-const gulp = require('gulp')
-const sass = require('gulp-sass')
-const concat = require('gulp-concat')
+const gulp = require('gulp');
+const sass = require('gulp-sass');
+const concat = require('gulp-concat');
+const cleanCSS = require('gulp-clean-css');
 
 gulp.task('styles', function(done) {
   gulp.src('styles/**/*.scss')
     .pipe(sass({
         errLogToConsole: true
     }))
+    .pipe(cleanCSS())
     .pipe(gulp.dest('./public/stylesheets/'))
     .pipe(concat('style.css'))
   done()
-})
+});

package.json

@@ -24,9 +24,6 @@
     "file-type": "^7.6.0",
     "glob": "7.1.1",
     "gm": "^1.23.1",
-    "gulp": "^4.0.2",
-    "gulp-concat": "^2.6.1",
-    "gulp-sass": "^4.0.2",
     "helmet": "^3.5.0",
     "i18n-2": "0.6.3",
     "log-timestamp": "latest",
@@ -52,6 +49,10 @@
     "ws": "3.3.1"
   },
   "devDependencies": {
+    "gulp": "^4.0.2",
+    "gulp-clean-css": "^4.3.0",
+    "gulp-concat": "^2.6.1",
+    "gulp-sass": "^4.0.2",
     "nodemon": "^2.0.6"
   },
   "main": "app.js",