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-lexer/cases/comments.pug

@@ -0,0 +1,29 @@
+
+// foo
+ul
+  // bar
+  li one
+  // baz
+  li two
+
+//
+  ul
+    li foo
+
+// block
+  // inline follow
+  li three
+
+// block
+  // inline followed by tags
+  ul
+    li four
+
+//if IE lt 9
+  // inline
+  script(src='/lame.js')
+  // end-inline
+
+p five
+
+.foo // not a comment