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/extend.js

@@ -0,0 +1,19 @@
+/**
+ * Module dependencies.
+ */
+
+var pug = require('../'),
+  path = __dirname + '/extend.pug',
+  str = require('fs').readFileSync(path, 'utf8'),
+  fn = pug.compile(str, {filename: path, pretty: true});
+
+var tobi = {name: 'tobi', age: 2};
+var loki = {name: 'loki', age: 1};
+var jane = {name: 'jane', age: 5};
+
+console.log(
+  fn({
+    title: 'pets',
+    pets: [tobi, loki, jane],
+  })
+);