chore: Add medusa-js README (#828)

packages/medusa-js/README.md

@@ -1 +1,49 @@
-# Medusa Commerce JS Client
+# Medusa JS Client
+
+[![Version](https://img.shields.io/npm/v/stripe.svg)](https://www.npmjs.org/package/@medusajs/medusa-js)
+
+The Medusa JS Client provides easy access to the Medusa API from a client written in Typescript.
+
+## Documentation
+
+See our [API reference](https://docs.medusa-commerce.com/api/store).
+
+## Installation
+
+Install the package with:
+
+```sh
+npm install @medusajs/medusa-js
+# or
+yarn add @medusajs/medusa-js
+```
+
+## Usage
+
+Import Medusa as a default import and initiate it:
+
+```js
+import Medusa from '@medusajs/medusa-js';
+
+const medusa = new Medusa();
+
+const { cart } = await medusa.carts.create({});
+```
+
+## Configuration
+
+### Initialize with config object
+
+The package can be initialized with several options:
+
+```js
+const medusa = new Medusa({
+  maxRetries: 3,
+  baseUrl: 'https://api.example.com',
+});
+```
+
+| Option       | Default                             | Description                               |
+| ------------ | ----------------------------------- | ----------------------------------------- |
+| `maxRetries` | `0`                                 | The amount of times a request is retried. |
+| `baseUrl`    | `'http://localhost:9000'`           | The url to which requests are made to     |