[archiso] README update

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

README

@@ -14,6 +14,7 @@ INDEX
 * Image types generated by mkarchiso.
 * File format for aitab.
 * Why the /isolinux and /arch/boot/syslinux directories?
+* Know issues
 * Building the most basic Arch Linux live media. (configs/baseline)
 * Building official Arch Linux live media. (configs/releng)
 
@@ -210,6 +211,15 @@ When make your custom boot-pendrive, you need to copy /arch directory to it.
 /isolinux/isolinux.cfg just holds /arch/boot/syslinux/syslinux.cfg
 
 
+*** Know issues
+
+** On shutdown there are two steps that [FAIL]:
+   "Unmounting Swap-backed Filesystems" and "Unmounting Non-API Filesystems",
+    These filesystem are in use at this stage by archiso, but...
+    This is not a real issue since, all mounted filesystem, loopback devices
+    and device mapper devices made by archiso will be "free" on "shutdown tmpfs"
+    (A.K.A deinitramfs), build at initramfs by [archiso_shutdown] initcpio hook.
+
 
 *** Building the most basic Arch Linux live media. (configs/baseline)