docs(isUndefined): Polish document styles and fix incorrect comments (#67)

* docs: add inline code markdown

* fix: change to undefined[] annotation

* Revert "fix: change to undefined[] annotation"

This reverts commit 3b81b8fb8a.

* chore: recommit

docs/ko/reference/predicate/isUndefined.md

@@ -1,6 +1,6 @@
 # isUndefined
 
-주어진 값이 undefined인지 확인해요.
+주어진 값이 `undefined`인지 확인해요.
 
 이 함수는 주어진 값이 `undefined` 인지 엄격 일치 (===) 기준으로 확인합니다.
 값이 `undefined` 이면 `true`, 아니면 `false` 를 반환해요.
@@ -15,11 +15,11 @@ function isUndefined(x: unknown): x is undefined;
 
 ### 파라미터
 
-- `x` (`unknown`): undefined인지 확인할 값
+- `x` (`unknown`): `undefined`인지 확인할 값
 
 ### 반환 값
 
-(`x is undefined`): 값이 undefined이면 true, 아니면 false.
+(`x is undefined`): 값이 `undefined`이면 `true`, 아니면 `false`.
 
 ## 예시
 

docs/reference/predicate/isUndefined.md

@@ -1,6 +1,6 @@
 # isUndefined
 
-Checks if the given value is undefined.
+Checks if the given value is `undefined`.
 
 This function tests whether the provided value is strictly equal to `undefined`.
 It returns `true` if the value is `undefined`, and `false` otherwise.
@@ -15,11 +15,11 @@ function isUndefined(x: unknown): x is undefined;
 
 ### Parameters
 
-- `x` (`unknown`): The value to test if it is undefined.
+- `x` (`unknown`): The value to test if it is `undefined`.
 
 ### Returns
 
-(`x is undefined`): True if the value is undefined, false otherwise.
+(`x is undefined`): `true` if the value is `undefined`, `false` otherwise.
 
 ## Examples
 

src/predicate/isUndefined.spec.ts

@@ -17,7 +17,7 @@ describe('isUndefined', () => {
 
     const result = arr.filter(isUndefined);
 
-    // Here the type of result should be `null[]`.
+    // Here the type of result should be `undefined[]`.
     expect(result).toStrictEqual([undefined]);
   });
 });