fix: add scoped error logging for lexer/parser errors

- Add std.log.scoped(.pugz) to template.zig and view_engine.zig
- Log detailed error info (code, line, column, message) when parsing fails
- Log template path context in ViewEngine on parse errors
- Remove debug print from lexer, use proper scoped logging instead
- Move benchmarks, docs, examples, playground, tests out of src/ to project root
- Update build.zig and documentation paths accordingly
- Bump version to 0.3.1

tests/sample_data/pug/examples/whitespace.pug

@@ -0,0 +1,11 @@
+- var js = '<script></script>'
+doctype html
+html
+ 
+  head
+    title= "Some " + "JavaScript"
+    != js
+   
+   
+     
+  body