Add Slang support

[antaalt]

Issue:

Here is a roadmap for getting Slang support into shader sense.

• Implement a validator which execute the slang compiler with rust binding (I believe shader-slang is the way to go) and parse its output.
• Implement symbol processing using tree-sitter-slang
• Add syntax highlighting for Slang with tmlanguages in shader-validator
• BONUS: Hide each language behind a cargo feature.