Swift lexer update for syntax highlight for macros and keywords

[manojmahapatra]

Hi,

I've reviewed the code of conduct. Here is a summary of the changes.

What is the issue?

• The Rouge syntax highlighter for Swift didn't recognize #expect from Swift Testing framework, treating it as a generic preprocessor instead of a testing assertion. Basically, the rule catches ANY line starting with # (except for ##, #", or #/) and treats the entire line as a preprocessor comment.

Changes

• Added a testing_macros set containing expect and require

• Modified the rule for # prefixed identifiers to check if they're Swift Testing macros

• Swift Testing macros (#expect, #require) are now highlighted as Name::Builtin

• Other Swift macros (like #selector) continue to be highlighted as Keyword

• Preprocessor directives (#if, #else, #endif) are properly handled in the :bol state

Testing

• Ran the the tests locally, looks alright.

[visionOS-amazon]

I'm curious what other directives there are that we should look for. For example #ifdef, #warning, #error.

[manojmahapatra]

I've intentionally tokenized #if and its relatives as preprocessor, but traditionally they're called as compiler directive in Swift land.

The rest like #warning, #error et al will be treated as Keyword as they'll not match to any rule.

[MikeMayer]

nit: whitespace added