[doc] Update README

Signed-off-by: Michael Brown <mcb30@ipxe.org>

README

@@ -1,8 +0,0 @@
-iPXE README File
-
-Quick start guide:
-
-   cd src
-   make
-
-For any more detailed instructions, see http://ipxe.org

README.md

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+iPXE network bootloader
+-----------------------
+
+[![Build](https://img.shields.io/github/actions/workflow/status/ipxe/ipxe/build.yml)](https://github.com/ipxe/ipxe/actions/workflows/build.yml?query=branch%3Amaster)
+[![Coverity](https://img.shields.io/coverity/scan/12130)](https://scan.coverity.com/projects/ipxe-ipxe)
+[![Release](https://img.shields.io/github/v/release/ipxe/ipxe)](https://github.com/ipxe/ipxe/releases/latest)
+
+iPXE is the leading open source network boot firmware. It provides a
+full PXE implementation enhanced with additional features such as:
+
+ - boot from a web server via HTTP or [HTTPS][crypto],
+
+ - boot from an iSCSI, FCoE, or AoE [SAN][sanboot],
+
+ - control the boot process with a [script][scripting],
+
+ - create interactive [forms][forms] and [menus][menus].
+
+You can use iPXE to replace the existing PXE ROM on your network card,
+or you can chainload into iPXE to obtain the features of iPXE without
+the hassle of reflashing.
+
+iPXE is free, open-source software licensed under the GNU GPL (with
+some portions under GPL-compatible licences).
+
+You can download the [rolling release binaries][rolling] (built from
+the latest commit), or use the most recent [stable release][release].
+
+For full documentation, visit the [iPXE website][ipxe].
+
+
+[crypto]: https://ipxe.org/crypto
+[forms]: https://ipxe.org/cmd/present
+[ipxe]: https://ipxe.org
+[menus]: https://ipxe.org/cmd/choose
+[release]: https://github.com/ipxe/ipxe/releases/latest
+[rolling]: https://boot.ipxe.org
+[sanboot]: https://ipxe.org/cmd/sanboot
+[scripting]: https://ipxe.org/scripting