Move tasks to separate files and simplify

gulp/tasks/validate.js

@@ -0,0 +1,13 @@
+const { src } = require('gulp');
+const config = require('../config');
+const plumber = require('../modules/plumber');
+const htmlValidator = require('gulp-w3c-html-validator');
+
+function validate() {
+  return src(config.dev + '**/*.html')
+    .pipe(plumber())
+    .pipe(htmlValidator())
+    .pipe(htmlValidator.reporter());
+}
+
+module.exports = validate;