Base: Add reboot(1) manpage

Base/usr/share/man/man1/reboot.md

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+## Name
+
+reboot - Reboot the machine
+
+## Synopsis
+
+```**sh
+$ reboot
+```
+
+## Description
+
+`reboot` instructs the kernel to reboot the machine immediately.
+
+## Notes
+
+The `reboot` utility opens the `/sys/firmware/power_state` node and writes the magic value "1"
+to instruct the kernel to reboot the machine.