Introduce collections interfaces and new methods to collections

What's Changed

Breaking Changes

• Introduce collections interfaces by @hugo-goncalves-kununu in #34

New Features

• Add FromIterable interface by @hugo-goncalves-kununu in #34
• Allow duplicates to return only unique values by @hugo-goncalves-kununu in #34
• Add keys and values method to collections by @hugo-goncalves-kununu in #34
• Add a method to test if a collection has an element by @tdashton in #32
• Add a method to find duplicate elements in a collection by @tdashton in #33

Full Changelog: v4.1.0...v5.0.0