Bump @rails/webpacker from 5.3.0 to 5.4.0

Bumps [@rails/webpacker](https://github.com/rails/webpacker) from 5.3.0 to 5.4.0.
- [Release notes](https://github.com/rails/webpacker/releases)
- [Changelog](https://github.com/rails/webpacker/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rails/webpacker/compare/v5.3.0...v5.4.0)

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

package.json

@@ -1,7 +1,7 @@
 {
   "dependencies": {
     "@fortawesome/fontawesome-free": "^5.15.3",
-    "@rails/webpacker": "^5.3.0",
+    "@rails/webpacker": "^5.4.0",
     "@sentry/browser": "^6.3.6",
     "bootstrap": "^4.6.0",
     "bootswatch": "^4.6.0",