Add GPL licensing

[ArcadeHustle]

This repo image is used by @michaelshmitty's Mr Fusion to distribute MiSter's linux subsystem. It needs proper licensing, and source code included.
https://github.com/MiSTer-devel/mr-fusion/blob/28bfc8877fb70ea7813d085614ef78ddea6a8786/scripts/create-sd-card-image.sh#L46

Please see the following example on how to add proper GPL legal info to this repo. MiSTer-devel/mr-fusion@434502f

As you can see below the license is not properly included with your distributed binary packages, in violation of GPL standards.

Extracting from release_20210316.rar

Creating    files                                                     OK
Creating    files/linux                                               OK
Extracting  files/linux/linux.img                                     OK 
Extracting  files/linux/MidiLink.INI                                  OK 
Creating    files/linux/mt32-rom-data                                 OK
Extracting  files/linux/mt32-rom-data/README                          OK 
Extracting  files/linux/ppp_options                                   OK 
Creating    files/linux/soundfonts                                    OK
Extracting  files/linux/soundfonts/README                             OK 
Extracting  files/linux/u-boot.txt_example                            OK 
Extracting  files/linux/uboot.img                                     OK 
Extracting  files/linux/updateboot                                    OK 
Extracting  files/linux/zImage_dtb                                    OK 
Extracting  files/linux/_samba.sh                                     OK 
Extracting  files/linux/_wpa_supplicant.conf                          OK 
Extracting  files/menu.rbf                                            OK 
Extracting  files/MiSTer                                              OK 
Extracting  files/MiSTer_example.ini                                  OK 
Creating    files/Scripts                                             OK
Extracting  files/Scripts/update.sh                                   OK 
Extracting  MiSTer SD Card Utility.exe                                OK 

./bin/lftpget:# This file is covered by GNU GPL. See file COPYING for details
./usr/share/unimaps/lat4u.uni:# Cepas <rch@pub.osf.lt>, 1997. Copying policy: GNU GPL V2.
./usr/share/vim/vim80/syntax/asciidoc.vim:" Licence:      GPL (http://www.gnu.org)
./usr/share/vim/vim80/syntax/initng.vim:" License:	GPL v2
./usr/share/zsh/5.3/functions/_zypper:# This file is released under the GPLv2.
./usr/share/zsh/5.3/functions/_osc:# This file is released under the GPLv2.
./usr/share/zsh/5.3/functions/_qdbus:# This file is released under the GPLv2.

[sorgelig]

added