ioquake3.html replaces Emscripten-generated HTML shell

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

code/web/empty/ioq3-config.json

@@ -0,0 +1,3 @@
+{
+    "files": []
+}