Compatible with DX11/Vulkan (Windows/Linux)

[funatsufumiya]

Sorry for very complicated PR. What was done is mainly descripted in README.md in my Win/Linux working branch.

This PR solves:

• Works on DX11/Vulkan (Windows/Linux). mainly fix Bug: Rendering Z-order is wrong on DX11/Vulkan #14
• Compiles shaders for DX11, SPIR-V, Metal ( ./scripts/shaders )
• Contain pre-compiled shaders (because specific types of shaders cannot be built on other platforms)
• Use unsigned short in index buffer: fix Enhancement: should treat unsigned short in index buffer #15
• Basic bgfx compatibility checking program in src/check
• ./scripts/start accept class name from argument (default fg.core if nothing given)
• Nushell (https://www.nushell.sh/) version of ./scripts/shaders and ./scripts/start (mainly for windows, still you can use git-bash as alternative)
• Upgrade LWJGL from 3.3.1 to 3.3.3
  • (FIY: probably we can upgrade to 3.3.6 smoothly. note that 3.3.4 and 3.3.5 has known bgfx rendering isssues on Win/Linux.)

Please consider to merge this, or edit (or ask me) anything you want.