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/check_list/auxiliary/includable.js

@@ -0,0 +1,8 @@
+var STRING_SUBSTITUTIONS = {
+  // table of character substitutions
+  '\t': '\\t',
+  '\r': '\\r',
+  '\n': '\\n',
+  '"': '\\"',
+  '\\': '\\\\',
+};