Import Luau lexer

[JakobDev]

This imports pygments.lexers.scripting.LuauLexer from Pygments.

Some notes:

• The generated XML file is not 100% valid as as some elements have 2 state attributes, but it does work
• I needed to tweak the import script to correctly convert the RegEx
• I needed to add OperatorReserved as a TokenType
• .luaurc is added as a filename to the JSON Lexer, as it's used by Luau

Implements #1062

[alecthomas]

Would it make more sense to integrate this into the Lua lexer?

[JakobDev]

Would it make more sense to integrate this into the Lua lexer?

Luau is based on Lua but it's a separate Language. See the documentation for more details.

Also Pygments has this as a separate lexer. It would be to much work to integrate this into the existing Lua lexer.