This commit introduces support for AST macros and templates, enabling
users to define and use custom, reusable components within the visual
DSL.
Key changes include:
- A new `MacroRegistry` to manage macro definitions.
- A `MacroExpander` to process macro calls and expand templates.
- A `MacroEvaluator` trait for evaluating expressions during expansion.
- The `Expansion` node in `BoundKind` to preserve the original macro
call and its expanded form for debugging.
- Updates to the `Binder`, `Dumper`, and `UpvalueAnalyzer` to handle the
new macro constructs.
- New examples demonstrating various macro functionalities like
`unless`, splicing, and nested macros.
Michael Schimmel