0.6.0-rc1 / 0.6.1-rc1

Now with serenity 0.12!

New features:

• ChoiceParameter is now not only a derive macro, but also a trait, so you can implement it manually (bc250b8)
• HelpConfiguration::include_description can be used to toggle whether a single command's help output includes its description, or only its help_text (0ad8ee6)

API updates:

• A lot of structs and enum are now #[non_exhaustive] to allow backwards compatible new features in the future (035e035, 6c08cfb, 1cbfeef)
• Command no longer has Default bounds on its generics (695ae1d)
• Changed some field types on Command to be more idiomatic (6c08cfb)
• CooldownTracker methods now take a dedicated user-constructable CooldownContext instead of Context<'_, U, E>, to make CooldownTracker usable outside poise internals ([bd73861](https://github.com/serenity-rs/poise/cMake ommit/bd73861d2679c26040353eba460d933c7d3a7a15))

Behavior changes:

• Rework of the help command to make it nicer (d38d226, d038ee6)

Detailed changelog: v0.5.7...v0.6.0

Thanks to @kangalio, @docwilco, @drwilco, @GnomedDev, @scottbot95!

Why "0.6.0-rc1 / 0.6.1-rc1"?

I (@kangalio) messed up when releasing. First, I prematurely released 0.6.0, which was buggy and had to be yanked. Then, bugs were fixed and I decided to push it as 0.6.0-rc1, thinking "ok we will release 0.6.0 properly this time, starting with rc's". However, cargo treats 0.6.0 as being semver-compatible to 0.6.0-rc1, hence even people depending on 0.6.0-rc1 were served the buggy 0.6.0 by cargo. No good. So I had to yank that too, and pushed the identical code as 0.6.1-rc1 instead.