[openstreetmap/openstreetmap-website] Added new Danger rule for catching outdated Gemfile.lock (PR #5301)

[Nenad Vujicic]

<!--
Please read the contributing guidelines before making a PR:
  https://github.com/openstreetmap/openstreetmap-website/blob/master/CONTRIBUTING.md

Pay particular attention to the section on how to present PRs:
  https://github.com/openstreetmap/openstreetmap-website/blob/master/CONTRIBUTING.md#pull-requests
-->

### Description
<!--Describe your changes in detail. If you have made changes to the UI, include screenshots. If your PR addresses a Github issue, please link to it.-->

Updated the Dangerfile by adding a new rule that checks if the Gemfile is updated while the Gemfile.lock is not, and if so, generates the "gemfile-lock-outdated" PR label.

![image](https://github.com/user-attachments/assets/5a54fb88-ddf5-4570-8272-de40baa1d1a0)

Created upon the [suggestion](https://github.com/openstreetmap/openstreetmap-website/pull/5295#issuecomment-2447849335).

### How has this been tested?
<!--Explain the steps you took to test your code.-->

Tested by running RuboCop locally and by committing changes to my personal fork before creating a problematic PR.
You can view, comment on, or merge this pull request online at:

  https://github.com/openstreetmap/openstreetmap-website/pull/5301

-- Commit Summary --

  * Added new Danger labeling rule

-- File Changes --

    M Dangerfile (10)

-- Patch Links --

https://github.com/openstreetmap/openstreetmap-website/pull/5301.patch
https://github.com/openstreetmap/openstreetmap-website/pull/5301.diff

-- 
Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/openstreetmap-website/pull/5301
You are receiving this because you are subscribed to this thread.

Message ID: <openstreetmap/openstreetmap-website/pull/5301 at github.com>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/rails-dev/attachments/20241104/6799f98b/attachment.htm>