Bump @appsignal/javascript from 1.3.31 to 1.4.0 in /frontend

Bumps [@appsignal/javascript](https://github.com/appsignal/appsignal-javascript/tree/HEAD/packages/javascript) from 1.3.31 to 1.4.0.
- [Release notes](https://github.com/appsignal/appsignal-javascript/releases)
- [Changelog](https://github.com/appsignal/appsignal-javascript/blob/main/packages/javascript/CHANGELOG.md)
- [Commits](https://github.com/appsignal/appsignal-javascript/commits/@appsignal/[email protected]/packages/javascript)

---
updated-dependencies:
- dependency-name: "@appsignal/javascript"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>