Initial commit: Pugz - Pug-like HTML template engine in Zig

Features:
- Lexer with indentation tracking and raw text block support
- Parser producing AST from token stream
- Runtime with variable interpolation, conditionals, loops
- Mixin support (params, defaults, rest args, block content, attributes)
- Template inheritance (extends/block/append/prepend)
- Plain text (piped, dot blocks, literal HTML)
- Tag interpolation (#[tag text])
- Block expansion with colon
- Self-closing tags (void elements + explicit /)
- Case/when statements
- Comments (rendered and silent)

All 113 tests passing.

.gitignore

@@ -0,0 +1,12 @@
+# Zig build artifacts
+zig-out/
+zig-cache/
+.zig-cache/
+
+# IDE
+.vscode/
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db