docs(api): add api doc

docs/README.md

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+**mutability** • [**Docs**](globals.md)
+
+***
+
+# mutability
+
+![Node CI](https://github.com/mutativejs/mutability/workflows/Node%20CI/badge.svg)
+[![npm version](https://badge.fury.io/js/mutability.svg)](http://badge.fury.io/js/mutability)
+![license](https://img.shields.io/npm/l/mutability)
+
+A JavaScript library for transactional mutable updates.
+
+## Motivation
+
+When we want to perform transactional updates on a mutable object, if an error is caught during the update process, the mutable update will not be applied at all. Otherwise, the mutable update will be applied to the mutable object. Therefore, we need a tool to implement this functionality.
+
+## Installation
+
+```sh
+yarn add mutative mutability
+```
+
+or with npm
+
+```sh
+npm install mutative mutability
+```
+
+## Usage
+
+```ts
+import { mutate } from 'mutability';
+
+test('base - mutate', () => {
+  const baseState = {
+    a: {
+      c: 1,
+    },
+  };
+  mutate(baseState, (draft) => {
+    draft.a.c = 2;
+  });
+  expect(baseState).toEqual({ a: { c: 2 } });
+});
+
+test('base - mutate with error', () => {
+  const baseState = {
+    a: {
+      c: 1,
+    },
+    b: {
+      c: 1,
+    },
+  };
+  try {
+    mutate(baseState, (draft) => {
+      draft.a.c = 2;
+      throw new Error('error');
+      draft.b.c = 2;
+    });
+  } catch (e) {
+    //
+  }
+  expect(baseState).toEqual({
+    a: {
+      c: 1,
+    },
+    b: {
+      c: 1,
+    },
+  });
+});
+```
+
+## License
+
+Mutability is [MIT licensed](https://github.com/mutativejs/mutability/blob/main/LICENSE).

docs/functions/mutate.md

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+[**mutability**](../README.md) • **Docs**
+
+***
+
+[mutability](../globals.md) / mutate
+
+# Function: mutate()
+
+> **mutate**\<`T`\>(`baseState`, `recipe`): `void`
+
+Transactional updates to the base state with the recipe.
+
+## Type parameters
+
+• **T**
+
+## Parameters
+
+• **baseState**: `T`
+
+• **recipe**
+
+## Returns
+
+`void`
+
+## Source
+
+[index.ts:7](https://github.com/mutativejs/mutability/blob/7716adccba23dd12347de1acf2bcc25ee5a2c9a6/src/index.ts#L7)

docs/globals.md

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+[**mutability**](README.md) • **Docs**
+
+***
+
+# mutability
+
+## Functions
+
+- [mutate](functions/mutate.md)