update gulp-htmlmin to latest

Author: jonchurch

package-lock.json

@@ -18,7 +18,7 @@
     "globby": "^6.1.0",
     "gulp": "^5.0.1",
     "gulp-cssnano": "^2.1.2",
-    "gulp-htmlmin": "^3.0.0",
+    "gulp-htmlmin": "^5.0.1",
     "gulp-imagemin": "^3.3.0",
     "gulp-purgecss": "^7.0.2",
     "gulp-responsive": "^2.11.0",