Feat/enum

[alanmachadozx]

Summary

This pull request adds the handling of the token enum, but needs to fix the hir

What changed

• implemented enum in parser
• added keyword "enum"
• create EnuDeclaration in ast

Validation

List the commands, tests, or manual checks you ran.

# example
cargo test

Documentation Impact

• No documentation changes were needed
• I updated the relevant documentation

Checklist

• My change is focused and reviewable
• I performed a self-review
• I added comments only where they help explain non-obvious logic
• I added or updated tests when applicable
• I ran the validation listed above
• I used the existing issue/PR templates where applicable