[doc] Add a minimal description and demo animation

Signed-off-by: Michael Brown <[email protected]>

README.md

@@ -5,4 +5,54 @@ wimboot: Windows Imaging Format bootloader
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+[`wimboot`][wimboot] is a boot loader for Windows Imaging Format
+`.wim` files.  It enables you to boot into a [Windows PE
+(WinPE)][winpe] deployment or recovery environment.
+
+You can use `wimboot` with [iPXE][ipxe] to [boot Windows PE via
+HTTP][howto].  With a Gigabit Ethernet network, a typical WinPE image
+should download in just a few seconds.
+
+Demo
+----
+
+This animation shows an HTTP network boot into the Windows 10
+installer.  The total elapsed time from power on to reaching the
+Windows installer screen is 17 seconds.
+
+![Demo animation](doc/demo.gif)
+
+Advantages
+----------
+
+### Speed
+
+`wimboot` can download images at the full speed supported by your
+network, since it can use HTTP rather than TFTP.
+
+### Ease of use
+
+`wimboot` works directly with `.wim` image files; there is no need to
+wrap your `.wim` into an ISO or FAT filesystem image.
+
+### BIOS/UEFI compatibility
+
+`wimboot` allows you to use a single configuration and set of files to
+boot under both BIOS and UEFI environments.
+
+License
+-------
+
+`wimboot` is free software licensed under the [GNU General Public
+License](LICENSE.txt).
+
+Quickstart
+----------
+
 See https://ipxe.org/wimboot for instructions.
+
+
+[wimboot]: https://ipxe.org/wimboot
+[ipxe]: https://ipxe.org
+[winpe]: https://en.wikipedia.org/wiki/Windows_Preinstallation_Environment
+[howto]: https://ipxe.org/howto/winpe