* Initial update to 1.21.3.
Compiles, launches, nothing tested yet.
* Boat tag includes chest boat tag.
* Avoid Material.values call.
* Split ride checks to separate event handler.
Bypass the interact entirely and let EntityMount handle it, since we can't discriminate usage in interact.
Old Bukkit code can still be found in the worldguard-legacy folder
and built with `gradle worldguard-legacy:build`. Hopefully nothing
got lost in the gradle-ization.