readme: qemu arm graphic link to question why virt does not have it

Author: cirosantilli

README.adoc

@@ -280,6 +280,8 @@ ____
 Most of the machines QEMU supports have annoying limitations (small amount of RAM, no PCI or other hard disk, etc) which are there because that's what the real hardware is like. If you don't care about reproducing the idiosyncrasies of a particular bit of hardware, the best choice today is the "virt" machine. This is a platform which doesn't correspond to any real hardware and is designed for use in virtual machines. It supports PCI, virtio, recent CPUs and large amounts of RAM. The only thing it doesn't have is graphics.
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+Me asking why: https://lists.gnu.org/archive/html/qemu-discuss/2018-05/msg00037.html
+
 We feel that this is a worthwhile tradeoff, since we expect most users don't care about graphics on typically embedded archs, and `virt` machines bring greater simplicity to this repo.
 
 If someone submits a well tested and documented graphics patch, we will consider it however. A good starting point, would be to: