Add sysutils/asmctl: Apple System Management Controller

Asmctl is a command line tool for Apple System Management Controller,
which controls the keyboard backlight and LCD backlight.

Assigning following key bindings work similar to Apple MacBook series.

WWW: https://github.com/yuichiro-naito/asmctl

PR: 225552
Submitted by: Yuichiro NAITO <naito.yuichiro@gmail.com>