feat(isNull): Add compatibility with lodash (#264)

* feat(isNull): Add isNull benchmark

* feat(isNull): Add compat's isNull test code

* docs(isNull): Update isNull status from 'review' to 'complete'

* Update src/compat/predicate/isNull.spec.ts

* Update src/compat/predicate/isNull.spec.ts

---------

Co-authored-by: Sojin Park <raon0211@toss.im>
Co-authored-by: Sojin Park <raon0211@gmail.com>

benchmarks/performance/isNull.bench.ts

@@ -0,0 +1,19 @@
+import { bench, describe } from 'vitest';
+import { isNull as isNullToolkit } from 'es-toolkit';
+import { isNull as isNullLodash } from 'lodash';
+
+describe('isNull', () => {
+  bench('es-toolkit/isNull', () => {
+    isNullToolkit(null);
+    isNullToolkit(undefined);
+    isNullToolkit('');
+    isNullToolkit(123);
+  });
+
+  bench('lodash/isNull', () => {
+    isNullLodash(null);
+    isNullLodash(undefined);
+    isNullLodash('');
+    isNullLodash(123);
+  });
+});

docs/compatibility.md

@@ -217,7 +217,7 @@ Even if a feature is marked "in review," it might already be under review to ens
 | [isNaN](https://lodash.com/docs/4.17.15#isNaN)                         | ❌                    |
 | [isNative](https://lodash.com/docs/4.17.15#isNative)                   | ❌                    |
 | [isNil](https://lodash.com/docs/4.17.15#isNil)                         | 📝                    |
-| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | 📝                    |
+| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | ✅                    |
 | [isNumber](https://lodash.com/docs/4.17.15#isNumber)                   | ❌                    |
 | [isObject](https://lodash.com/docs/4.17.15#isObject)                   | ❌                    |
 | [isObjectLike](https://lodash.com/docs/4.17.15#isObjectLike)           | ❌                    |

docs/ko/compatibility.md

@@ -218,7 +218,7 @@ chunk([1, 2, 3, 4], 0);
 | [isNaN](https://lodash.com/docs/4.17.15#isNaN)                         | ❌        |
 | [isNative](https://lodash.com/docs/4.17.15#isNative)                   | ❌        |
 | [isNil](https://lodash.com/docs/4.17.15#isNil)                         | 📝        |
-| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | 📝        |
+| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | ✅        |
 | [isNumber](https://lodash.com/docs/4.17.15#isNumber)                   | ❌        |
 | [isObject](https://lodash.com/docs/4.17.15#isObject)                   | ❌        |
 | [isObjectLike](https://lodash.com/docs/4.17.15#isObjectLike)           | ❌        |

docs/zh_hans/compatibility.md

@@ -217,7 +217,7 @@ chunk([1, 2, 3, 4], 0);
 | [isNaN](https://lodash.com/docs/4.17.15#isNaN)                         | ❌       |
 | [isNative](https://lodash.com/docs/4.17.15#isNative)                   | ❌       |
 | [isNil](https://lodash.com/docs/4.17.15#isNil)                         | 📝       |
-| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | 📝       |
+| [isNull](https://lodash.com/docs/4.17.15#isNull)                       | ✅       |
 | [isNumber](https://lodash.com/docs/4.17.15#isNumber)                   | ❌       |
 | [isObject](https://lodash.com/docs/4.17.15#isObject)                   | ❌       |
 | [isObjectLike](https://lodash.com/docs/4.17.15#isObjectLike)           | ❌       |

src/compat/predicate/isNull.spec.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+import { isNull } from '../../predicate';
+import { falsey } from '../_internal/falsey';
+
+/**
+ * @see https://github.com/lodash/lodash/blob/main/test/isNull.spec.js
+ */
+describe('isNull', () => {
+  it('should return `true` for `null` values', () => {
+    expect(isNull(null)).toBe(true);
+  });
+
+  it('should return `false` for non `null` values', () => {
+    const expected = falsey.map(value => value === null);
+    const actual = falsey.map((value, index) => (index ? isNull(value) : isNull(undefined)));
+
+    // eslint-disable-next-line
+    (function (..._args: any[]) {
+      // eslint-disable-next-line
+      expect(isNull(arguments)).toBe(false);
+    })(1, 2, 3);
+    expect(actual).toEqual(expected);
+    expect(isNull([1, 2, 3])).toBe(false);
+    expect(isNull(true)).toBe(false);
+    expect(isNull(new Date())).toBe(false);
+    expect(isNull(new Error())).toBe(false);
+    expect(isNull(Array.prototype.slice)).toBe(false);
+    expect(isNull({ a: 1 })).toBe(false);
+    expect(isNull(1)).toBe(false);
+    expect(isNull(/x/)).toBe(false);
+    expect(isNull('a')).toBe(false);
+    expect(isNull(Symbol('a'))).toBe(false);
+    expect(isNull(undefined)).toBe(false);
+  });
+});