Third-party crates are crates that aren't supported by the Twilight organization but are recognised by it. Of course, use these at your own risk. :)
Third-party crates may become first-party crates if they end up becoming useful enough for a large number of users.
Below is a list of crates. If you want yours added, feel free to ask!
twilight-interactions provides macros and utilities to make interactions easier to use.
Its features include slash command parsing and creation from structs with derive macros.