Add scripts/secpick

What does this MR do?

Related to: #714 (closed)

This is basically a copy'n'paste from Gitlab's secpick (https://gitlab.com/gitlab-org/gitlab/-/blob/master/bin/secpick).

Questions/Information

1. Is it ok to be a Ruby script?
   • I think so, since it's just a development helper
2. I removed external dependencies (gems) from the script avoid ruby-dependencies management in this project.
3. Is it ok to be in the scripts folder? (the Gitlab's one is in bin)
   • I think so, since go populates the bin folder and we already have scripts/security-harness

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines