Automate monthly browserslist-db update via scheduled GitHub Actions workflow

[florian-sanders-cc]

Context

We should automate the monthly update of the browserslist database to keep our browser support data current.

Proposed Solution

Create a GitHub Actions scheduled workflow that:

1. Runs on the 1st of each month (cron: 0 0 1 * *)
2. Executes npx update-browserslist-db@latest (only modifies package-lock.json)
3. Creates a PR with a chore commit (e.g., chore(deps): update browserslist-db)
4. Assigns the team as reviewers

Implementation Notes

• Use peter-evans/create-pull-request action for PR creation (Note: Let's avoid using an action for this, it should be easy to do by ourselves really).
• Will need to use a PAT or GitHub App token (not GITHUB_TOKEN) if we want CI workflows to trigger on the created PR
• The existing CI_TOKEN secret could potentially be reused

References

• update-browserslist-db
• peter-evans/create-pull-request

/cc @Galimede @florian-sanders-cc