Update dependency gscan to v6.4.0 (#555)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -94,7 +94,7 @@
         "autoprefixer": "10.5.0",
         "beeper": "2.1.0",
         "cssnano": "8.0.2",
-        "gscan": "6.3.0",
+        "gscan": "6.4.0",
         "gulp": "5.0.1",
         "gulp-concat": "2.6.1",
         "gulp-livereload": "4.0.2",