build(deps): bump async from 3.2.3 to 3.2.4 in /src

Bumps [async](https://github.com/caolan/async) from 3.2.3 to 3.2.4.
- [Release notes](https://github.com/caolan/async/releases)
- [Changelog](https://github.com/caolan/async/blob/master/CHANGELOG.md)
- [Commits](https://github.com/caolan/async/compare/v3.2.3...v3.2.4)

---
updated-dependencies:
- dependency-name: async
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

src/package.json

@@ -30,7 +30,7 @@
     }
   ],
   "dependencies": {
-    "async": "^3.2.2",
+    "async": "^3.2.4",
     "clean-css": "^5.3.2",
     "cookie-parser": "^1.4.6",
     "cross-spawn": "^7.0.3",