Add prerequisites to scale-generator

[theomelo]

References: #984

Adds prerequisite to Scale Generator exercise.

[github-actions]

Dear theomelo

Thank you for contributing to the JavaScript track on Exercism! 💙
You will see some automated feedback below 🤖. It would be great if you can make sure your PR covers those points. This will save your reviewer some time and your change can be merged quicker.

• ✍️ If your PR is not related to an existing issue (and is not self-explaining like a typo fix), please make sure the description explains why the change you made is necessary.

• 🔤 If your PR fixes an easy to identify typo, if would be great if you could check for that typo in the whole repo. For example, if you found Unicdoe, use "replace all" in your editor (or command line magic) to fix it consistently.

Dear Reviewer/Maintainer

• 📏 Make sure you set the appropriate x:size label for the PR. (This also works after merging, in case you forgot about it.)

• 🔍 Don't be too nit-picky. If the PR is a clear improvement compared to the status quo, it should be approved as clear signal this is good to be merged even if the minor comments you might have are not addressed by the contributor. Further improvement ideas can be captured in issues (if important enough) and implemented via additional PRs.

• 🤔 After reviewing the diff in the "Files changed" section, take a moment to think about whether there are changes missing from the diff. Does something need to be adjusted in other places so the code or content stays consistent?

_{Automated comment created by PR Commenter 🤖.}

[theomelo]

@junedev, this is my first time contributing to this project. Would you confirm if my changes make sense? 🙏

[junedev]

I am sorry but I will have to put this on hold for now.

Here the official note about this:

We are currently in a phase of our journey where we have paused community contributions to allow us to take a breather and redesign our community model. You can learn more in this blog post. As such, all issues and PRs in this repository are being closed.

That doesn't mean we're not interested in your ideas, or that if you're stuck on something we don't want to help. The best place to discuss things is with our community on the Exercism Community Forum. You can use this link to copy this into a new topic there.