Now lwext4 is ready, and qemu-virt64-riscv smart can boot with rootfs.
Updated README to introduce this.
This patch also replace qemu-nographic.sh with run.sh, which has a more
simple name and more robust to launch rootfs image binary.
TBD: qemu-nographic.bat is not touched, hope some guys from Windows can
give a hand.
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
