archived prebuilts used by pygbag runtime.

Content per version folder :

• Xterm.js 5.1+ sixel addon
• libpython wasm from current CPython release 3.11.x serie and 3.12(git)
• pymain with Panda3D modules facilitating access to emscripten ecosystem.
• a minimal emscripten MEMFS filesystem that contains minimal stdlib
• BrowserFS a library to extend above filesystem to support zip archives and read/write overlays.
• a "site" pythonrc.py that patch some modules for the wasm platform and take care of running main() in a async way
• some js glue (pythons.js) to load everything above