Add keyboard shortcut for commenting back in

[systimotic]

Pre-Submission Checklist

• Your pull request targets the staging branch of FreeCodeCamp.
• Branch starts with either fix/, feature/, or translate/ (e.g. fix/signin-issue)
• You have only one commit (if not, squash them into one commit).
• All new and existing tests pass the command npm run test-challenges. Use git commit --amend to amend any fixes.

Type of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)
• Add new translation (feature adding new translations)

Checklist:

• Tested changes locally.
• Closes currently open issue (replace XXXX with an issue no): Closes #XXXX

Description

On the live site, pressing Ctrl or Cmd + / comments and uncomments the code. I really love this feature. This functionality is no longer present in the beta. I did a little bit of git-digging, but I wasn't able to find where it disappeared. I decided to try to add it back in, and see if it would work. Surprisingly, it worked fine! Credits to @gangachris for originally adding this in #9854 👍
Edit: I wasn't sure whether this was a feature or a fix.

[Bouncey]

The changes look good, I will pull this done shortly to test.

[Bouncey]

LGTM 👍

Thanks for contributing 🎉