feat(unit/timer_unit) :First step implementation of timer unit #41 (#44)

实现timer类型的unit

Co-authored-by: BrahmaMantra <2033552517.qq.com>

添加systemctl查看系统服务状态 (#27)

* 解决warning

* 几个简单的systemctl命令

* 添加systemctl查看系统服务状态