Added custom.cfg for loading Windows 8 (EFI)

win/custom.cfg

+# Taken from https://github.com/GAireg/grubconfig/blob/master/grub.cfg
+# load windows from efi
+menuentry "Windows EFI" {
+	search --file --set dev_root --no-floppy /EFI/Microsoft/boot/bootmgfw.efi
+	chainloader ($dev_root)/EFI/Microsoft/boot/bootmgfw.efi
+}
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