Add examples

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Idea: Translate "example" folder of raylib from C to Lua

• core (done partially)
• shapes (done partially)
• textures (done partially)
• text (done partially)
• models
• audio
• shaders
• physics

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References:

• https://github.com/raysan5/raylib-lua/tree/master/examples
• https://github.com/RobLoach/raylib-lua-sol/tree/master/examples

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Status:
A few example files were translated to Lua, which (imo) would be enough for demonstration.
(Reopen this issue if we need more examples?)