Provide a small(er than Firefox) graphical app as an example

[ThibaultLemaire]

Firefox is a big beast (and potentially not the safest to run, see #53), I thought I would find a smaller package to demonstrate graphical apps.

Here are some patches to apply to the README (I'm sorry I was too lazy to setup a whole fork and RSA keys, etc. I hope you don't mind.)

I also found a game to showcase SDL compat as well. (As a wannabe indie game developer who doesn't want to bother with packaging for every Linux distro out there, I'm very interested in SDL support. I thought others might be too.)

[matthewbauer]

Looks good, applied in d623276 and 83742ac.

[ThibaultLemaire]

For the record, I've successfully tested xskat and ivan executables on NixOS 20.09 (Nightingale) x86_64 (The machine that bundled them), Debian GNU/Linux 9 (stretch) 64-bitas well asManjaro KDE 20.0.3` (VM). I couldn't get them to work with Fedora (VM). I suspect that's to do with wayland and/or kernel permissions. I'll have to do some more tests.