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/eachOf/__snapshots__/index.test.js.snap

@@ -0,0 +1,5 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Proper Usage Brackets 1`] = `"<li>a</li><li>b</li><li>foo</li><li>bar</li>"`;
+
+exports[`Proper Usage No Brackets 1`] = `"<li>a</li><li>b</li><li>foo</li><li>bar</li>"`;

tests/sample_data/pug/test/eachOf/error/left-side.pug

@@ -0,0 +1,3 @@
+each [key, val of users
+  li= key
+  li= val

tests/sample_data/pug/test/eachOf/error/no-brackets.pug

@@ -0,0 +1,3 @@
+each key, val of users
+  li= key
+  li= val

tests/sample_data/pug/test/eachOf/error/one-val.pug

@@ -0,0 +1,3 @@
+each [key] of users
+  li= key
+  li= val

tests/sample_data/pug/test/eachOf/error/right-side.pug

@@ -0,0 +1,3 @@
+each key, val] of users
+  li= key
+  li= val

tests/sample_data/pug/test/eachOf/index.test.js

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+const pug = require('../../');
+
+describe('Inproper Usage', () => {
+  test('Only left-side bracket', () => {
+    expect(() => pug.compileFile(__dirname + '/error/left-side.pug')).toThrow(
+      'The value variable for each must either be a valid identifier (e.g. `item`) or a pair of identifiers in square brackets (e.g. `[key, value]`).'
+    );
+  });
+  test('Only right-side bracket', () => {
+    expect(() => pug.compileFile(__dirname + '/error/right-side.pug')).toThrow(
+      'The value variable for each must either be a valid identifier (e.g. `item`) or a pair of identifiers in square brackets (e.g. `[key, value]`).'
+    );
+  });
+  test('Only one value inside brackets', () => {
+    expect(() => pug.compileFile(__dirname + '/error/one-val.pug')).toThrow(
+      'The value variable for each must either be a valid identifier (e.g. `item`) or a pair of identifiers in square brackets (e.g. `[key, value]`).'
+    );
+  });
+  test('No brackets', () => {
+    expect(() => pug.compileFile(__dirname + '/error/no-brackets.pug')).toThrow(
+      'The value variable for each must either be a valid identifier (e.g. `item`) or a pair of identifiers in square brackets (e.g. `[key, value]`).'
+    );
+  });
+});
+describe('Proper Usage', () => {
+  test('Brackets', () => {
+    const html = pug.renderFile(__dirname + '/passing/brackets.pug', {
+      users: new Map([
+        ['a', 'b'],
+        ['foo', 'bar'],
+      ]),
+    });
+    expect(html).toMatchSnapshot();
+  });
+  test('No Brackets', () => {
+    const html = pug.renderFile(__dirname + '/passing/no-brackets.pug', {
+      users: new Map([
+        ['a', 'b'],
+        ['foo', 'bar'],
+      ]),
+    });
+    expect(html).toMatchSnapshot();
+  });
+});

tests/sample_data/pug/test/eachOf/passing/brackets.pug

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+each [key, val] of users
+  li= key
+  li= val

tests/sample_data/pug/test/eachOf/passing/no-brackets.pug

@@ -0,0 +1,3 @@
+each data of users
+  li= data[0]
+  li= data[1]