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/duplicate-block/index.test.js

@@ -0,0 +1,10 @@
+const pug = require('../../');
+
+test('layout with duplicate block', () => {
+  const outputWithAjax = pug.renderFile(__dirname + '/index.pug', {ajax: true});
+  const outputWithoutAjax = pug.renderFile(__dirname + '/index.pug', {
+    ajax: false,
+  });
+  expect(outputWithAjax).toMatchSnapshot();
+  expect(outputWithoutAjax).toMatchSnapshot();
+});