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/code.js

@@ -0,0 +1,15 @@
+/**
+ * Module dependencies.
+ */
+
+var pug = require('../'),
+  path = __dirname + '/code.pug',
+  str = require('fs').readFileSync(path, 'utf8'),
+  fn = pug.compile(str, {filename: path, pretty: true});
+
+var users = {
+  tj: {age: 23, email: 'tj@vision-media.ca', isA: 'human'},
+  tobi: {age: 1, email: 'tobi@is-amazing.com', isA: 'ferret'},
+};
+
+console.log(fn({users: users}));