Bump @vue/cli-plugin-babel from 4.5.15 to 5.0.8 in /frontend

Bumps [@vue/cli-plugin-babel](https://github.com/vuejs/vue-cli/tree/HEAD/packages/@vue/cli-plugin-babel) from 4.5.15 to 5.0.8.
- [Release notes](https://github.com/vuejs/vue-cli/releases)
- [Changelog](https://github.com/vuejs/vue-cli/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vue-cli/commits/v5.0.8/packages/@vue/cli-plugin-babel)

---
updated-dependencies:
- dependency-name: "@vue/cli-plugin-babel"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

frontend/package.json

@@ -22,7 +22,7 @@
     "vue-socket.io": "^3.0.10"
   },
   "devDependencies": {
-    "@vue/cli-plugin-babel": "~4.5.15",
+    "@vue/cli-plugin-babel": "~5.0.8",
     "@vue/cli-plugin-eslint": "~4.5.15",
     "@vue/cli-plugin-pwa": "~4.5.15",
     "@vue/cli-plugin-router": "~5.0.4",