Update dependency html-minifier to v4 (#90)

Author: renovate[bot]

package-lock.json

@@ -65,7 +65,7 @@
     "gulp-uglify": "^3.0.0",
     "gulp-useref": "^3.1.3",
     "gulp-zip": "^5.0.0",
-    "html-minifier": "^3.5.16",
+    "html-minifier": "^4.0.0",
     "html-to-text": "^5.0.0",
     "idb": "^3.0.2",
     "ini": "^1.3.4",