Bump @rails/webpacker from 4.2.2 to 5.2.1

Bumps [@rails/webpacker](https://github.com/rails/webpacker) from 4.2.2 to 5.2.1.
- [Release notes](https://github.com/rails/webpacker/releases)
- [Changelog](https://github.com/rails/webpacker/blob/master/CHANGELOG.md)
- [Commits](rails/webpacker@v4.2.2...v5.2.1)

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

package.json

@@ -2,7 +2,7 @@
   "name": "suikoden-election-2018",
   "private": true,
   "dependencies": {
-    "@rails/webpacker": "4.2.2",
+    "@rails/webpacker": "5.2.1",
     "axios": "^0.21.1",
     "vue": "^2.6.11",
     "vue-loader": "15.9.6",