Update README and LICENSE files

Add history of RGBDS and original license.

Signed-off-by: AntonioND <antonio_nd@outlook.com>

LICENSE.md

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+# Original code
+
+Copyright (C) 1997  Carsten Sorensen <surfsmurf@matilde.demon.co.uk>
+
+The ASMotor package (xAsm, xLink, RGBFix, examples and documentation) is
+freeware and distributed as is. The author retains his copyright and right to
+modify the specifications and operation of the software without notice.
+
+In other words this means I encourage you to...
+
+- use it for whatever purpose even professional work without me charging you a
+  penny
+- copy it to another person (wholly or in part, though I'm sure he'd appreciate
+  the whole package) in whatever form you find suitable
+- mass-distribute the ASMotor package if it is complete (xAsm, xLink, RGBFix and
+  documentation).
+- contact me if you have any problems
+
+This also means you can't...
+
+- blame me for loss of profit, data, sleep, food or other nasty things through
+  the use or distribution of ASMotor. If you choose to use ASMotor  you do so at
+  your own risk.
+- expect me to be able to help you should you have a problem related or not to
+  ASMotor.
+
+# Otaku no Zoku's modifications
+
+Copyright (C) 1999  Justin Lloyd <jlloyd@imf.la> (?)
+
+                      DO WHATEVER PUBLIC LICENSE*
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. You can do whatever you want to with the work.
+  1. You cannot stop anybody from doing whatever they want to with the work.
+  2. You cannot revoke anybody elses DO WHATEVER PUBLIC LICENSE in the work.
+
+ This program is free software. It comes without any warranty, to
+ the extent permitted by applicable law. You can redistribute it
+ and/or modify it under the terms of the DO WHATEVER PUBLIC LICENSE
+
+ Software originally created by Justin Lloyd @ http://otakunozoku.com/
+
+# rgbds-linux
+
+Copyright (C) 2009  Vegard Nossum <vegard.nossum@gmail.com>
+
+# Current
+
+rgbasm and rgblink are derived from Justin Lloyd's RGBDS.
+
+rgbfix was rewritten from scratch by Anthony J. Bentley, and is released
+under the ISC license; see the source file for the text of the license.
+
+rgbgfx was written by stag019, and is released under the ISC license.
+
+Some files of rgblink were written by Antonio Niño Díaz, and they are relased
+under the ISC license. The affected files have the appropriate license in the
+header of the file.
+
+The UTF-8 decoder in src/asm/charmap.c was written by Björn Höhrmann and is
+released under the MIT license. The remainder of charmap.c was written by
+stag019, and is released under the ISC license.
+
+extern/err.c is derived from the Musl C library, http://www.musl-libc.org,
+and is released under the MIT license.
+
+extern/reallocarray.c is derived from the OpenBSD Project,
+http://www.openbsd.org, and is released under the ISC license.
+
+extern/strl.c is derived from the OpenBSD Project, http://www.openbsd.org,
+and is released under the BSD license.