Feat/preprocessor

[Sarrus1]

Add preprocessing support to the LSP to support macro expansion and #if conditions which break the tree-sitter grammar.

• [x] Create a SourcePawn lexer in Rust.
• [x] Write an expression evaluator with the same operators precedence as SourcePawn.
• [x] Write a literal parser.
• [x] Handle define expansion in the evaluator.
• [x] Handle define expansion in the code.
• [x] Do the same for macros.
• [x] Handle define/macro expansion column shift.
• [x] Write a conditional code writer that is compatible with tree-sitter.
• [x] Handle errors.
• [x] Report errors.
• [x] Handle #include statements.
• [x] Report the range of ignored define identifiers to the lsp.
• [x] Grey out ignored code.
• [x] Add #elseif support.