Also make viewing client.html directly use client-config.json in the
same directory so it's possible to "live edit" both the files without
having to run make.
List files for multiple games in a single client-config.json file so
that com_basegame argument can pick different game data.
Use ioquake3.html?com_basegame=demoq3 (or tademo) to run the Quake 3 or
Team Arena demo. They require new QVMs from baseq3/missionpack to run.
Modify the client HTML file when copying it to the build directory to
apply current CLIENTBIN and BASEGAME. It always loads engine/data from
the current directory (no need to try to locate the build directory).
This enables several things:
* Optionally load pk3 files from a web server at runtime instead of bundling them with Emscripten at build time
* Set command line arguments via URL param
* It's not ugly
