Add ShowSecondsInClock as part of the setting Explorer settings

It may be a minor addition but having this show in the taskbar has been a setting that I've enabled on all my devices over the years as is very useful for quick glances at the time & allows for questions you may have like

• I wanna spend just 90s on this section
• Did that process startup /command complete slower this time than last
• Toliet break timing
• Pre-meeting timing countdowns too

etc etc

Issue 中没有指定文件或测试。首先定位现有的 Explorer 设置入口以及设置的声明方式，然后将 ShowSecondsInClock 添加到其中。完成的标准是：该设置与其他 Explorer 设置一起提供，并启用 Windows 任务栏时钟中的秒数显示。