Scaffold vpinball-wasm: Emscripten port of Visual Pinball

Build scripts, CMake/source patches, npm packaging, and a Gitea CI
workflow to compile the real Visual Pinball engine (SDL3 + WebGL2 +
libwinevbs for real VBScript) to WebAssembly.

The patches are validated end-to-end: the patched engine boots in a
real browser, loads a real .vpx table, compiles its real GLSL shaders,
computes environment map radiance, initializes physics, and starts the
VBScript engine, before hanging on the one deliberately-deferred piece
of work (game loop rewrite around emscripten_set_main_loop), documented
in the README's roadmap.

.gitignore

@@ -0,0 +1,7 @@
+/vendor/
+/build/
+/dist/
+/node_modules/
+/emsdk
+*.log
+.DS_Store