Add support for the :kind command in the REPL

[Gedochao]

The :kind command was (and is) supported by the Scala 2 REPL, while it is missing in Scala 3.

scala -S 2.13
Welcome to Scala 2.13.15 (OpenJDK 64-Bit Server VM, Java 17).
Type in expressions for evaluation. Or try :help.

scala> :help
All commands can be abbreviated, e.g., :he instead of :help.
(...)
:kind [-v] <type>        display the kind of a type. see also :help kind
(...)

scala> :kind Int
Int's kind is A

scala> :kind List
List's kind is F[+A]