This follows some recent discussions around the project's philosophy
and which fan-made hacks are supported (specifically the Doom
v1.91 / -longtics feature). It's worth providing some explicit
guidance as to why this feature is supported, while other executable
hacks are not.
Some of the features of this new clause are not yet implemented (the
-strictdemos flag and the warnings when playing non-vanilla demos).
This is part of #817. Thanks to @AXDOOMER for challenging some of the
perceived inconsistencies in the project philosophy and inspiring me
to explain this in a more rational/structured way.
We are now working to emulate older (pre-v1.9) Doom versions, so it
is worth clarifying the goals of the project slightly.
Also add Chex Quest to the list of games.
