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/test/shadowed-block/__snapshots__/index.test.js.snap

@@ -0,0 +1,5 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`layout with shadowed block 1`] = `"<!-- layout.pug: root--><!-- index.pug: shadowed-->"`;
+
+exports[`layout with shadowed block 2`] = `"<!-- layout.pug: root--><!-- index.pug: shadowed-->"`;