docs(MapKeys): Add MapKeys type documentation

docs/ko/reference/map/MapKeys.md

@@ -0,0 +1,32 @@
+# MapKeys\<T>
+
+## 개요
+
+주어진 Map 타입 `T`로 부터 키 타입을 추출해요.
+
+## 문법
+
+```ts
+type MapKeys<T extends Map<unknown, unknown>> =
+  T extends Map<infer K, unknown> ? K : never;
+```
+
+- **T**: 키 타입을 추출할 Map 타입이에요.
+
+## 예제
+
+```ts
+const phoneBook: Map<'tomas' | 'sha', string> = new Map([
+ ['tomas': '010-0000-0000'],
+ ['sha': '010-1111-1111'],
+])
+
+type PhoneBookKeys = MapKeys<typeof phoneBook>; // 'tomas' | 'sha'
+
+const hashMap: Map<string, string> = new Map([
+ ['0': 'coffee'],
+ ['1': 'dessert']
+])
+
+type HashMapKeys = MapKeys<typeof hashMap>; // string
+```

docs/reference/map/MapKeys.md

@@ -0,0 +1,32 @@
+# MapKeys\<T>
+
+## Overview
+
+Extracts the key type from a given map type `T`.
+
+## Syntax
+
+```ts
+type MapKeys<T extends Map<unknown, unknown>> =
+  T extends Map<infer K, unknown> ? K : never;
+```
+
+- **T**: The map type from which to extract the key type.
+
+## Examples
+
+```ts
+const phoneBook: Map<'tomas' | 'sha', string> = new Map([
+ ['tomas': '010-0000-0000'],
+ ['sha': '010-1111-1111'],
+])
+
+type PhoneBookKeys = MapKeys<typeof phoneBook>; // 'tomas' | 'sha'
+
+const hashMap: Map<string, string> = new Map([
+ ['0': 'coffee'],
+ ['1': 'dessert']
+])
+
+type HashMapKeys = MapKeys<typeof hashMap>; // string
+```