chore: Script for getting an up-to-date list of avail. devfiles

[rkratky]

What does this pull request change?

Adds tools/devfiles-list.sh

What issues does this pull request fix or reference?

https://issues.redhat.com/browse/RHDEVDOCS-4164

Specify the version of the product this pull request applies to

3.x+

Pull Request checklist

The author and the reviewers validate the content of this pull request with the following checklist, in addition to the automated tests.

• Any procedure:
  • [ x ] Successfully tested.
• Any page or link rename:
  • [ x ] The page contains a redirection for the previous URL.
  • Propagate the URL change in:
    • [ x ] Dashboard default branding data
    • [ x ] Chectl constants.ts
• [ x ] Builds on Eclipse Che hosted by Red Hat.
• [ x ] the Validate language on files added or modified step reports no vale warnings.

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[themr0c]

Please rebase, it should fix the build.