Add lexer for Slang

[Tearnote]

Is there an existing issue for this?

• I have searched the existing issues

What is the missing lexer?

I'd greatly appreciate a lexer for Slang, the GPU shading language now adopted by Khronos Group:
https://shader-slang.org/

Links to existing syntax definitions

There is a tree-sitter grammar: https://github.com/tree-sitter-grammars/tree-sitter-slang
As it's mostly a superset of HLSL, it would be a great start.