add support for F5OS

[teunvink]

Pre-Request Checklist

• [ ] Passes rubocop code analysis (try rubocop --auto-correct)
• [ ] Tests added or adapted (try rake test)
• [x] Changes are reflected in the documentation
• [x] User-visible changes appended to CHANGELOG.md

Description

Add support for F5OS (F5 appliances and chassis).