Add windows to boot menu

well, you’re not technically supposed to have two ESPs on one physical drive, which is why Windows will install its ESP to an existing one if you try to dual boot on the same drive. But the 100M ESP that Windows makes if you install it first isn’t very big, which is why we now have support for xbootldr with systemd-boot. If Windows and systemd-boot share an ESP, systemd-boot will show Windows.