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/cases/include.script.html

@@ -0,0 +1,6 @@
+<script id="pet-template" type="text/x-template">
+  <div class="pet">
+    <h1>{{name}}</h1>
+    <p>{{name}} is a {{species}} that is {{age}} old</p>
+  </div>
+</script>