Added a README

README

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+===============
+*** Colonel ***
+===============
+This is a small OS project I'm working on. It's slow progress and
+probably shouldn't be run anywhere except in an emulator. It currently
+supports the following architectures:
+ - x86
+
+# Compiling
+-----------
+You'll want to setup a cross-compilation toolchain with GCC
+(https://gcc.gnu.org/) for your target architecture, along with
+GNU Make (https://www.gnu.org/software/make/) (I'll switch to the
+GNU autotools as soon as I can get them to work properly).
+
+To compile a full image you can run `make build-iso`, which will use
+GNU GRUB (https://www.gnu.org/software/grub/) as the bootloader. Else,
+just run `make` and it will build the kernel into a file called
+`colonel.bin`. You can run the latter with QEMU (https://www.qemu.org/)
+by using the `-kernel` option.
+
+# License
+---------
+This project is licensed under the terms and conditions of the GNU
+General Public License version 3 or greater (/LICENSE).