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/text.pug

@@ -0,0 +1,46 @@
+option(value='') -- (selected) --
+
+p
+
+p.
+
+p
+  | foo
+  | bar
+  |
+  | 
+  | baz
+
+p.
+  foo
+
+
+  bar
+  baz
+
+.
+
+.
+  foo
+
+
+  bar
+  baz
+
+pre
+  | foo
+  |   bar
+  |     baz
+  | .
+
+pre.
+  foo
+    bar
+      baz
+  .
+
+.
+  foo
+    bar
+      baz
+  .