v0.21.0 - the "Groups are just slices" release

Group is now a type instead of a function, which is technically a breaking change, but is not expected to impact many codebases, if any at all. Special thanks to @deitrix for suggesting this design! 😎

What's Changed

• Drop support for Go 1.16 and Go 1.17 by @markuswustenberg in #203
• Add full example app by @markuswustenberg in #204
• Make Group a type by @markuswustenberg in #202
• Use go workspace in example app by @markuswustenberg in #211

Full Changelog: v0.20.5...v0.21.0