docs(common): CHECKOUT-2738 Update README with usage instructions

Author: davidchin

README.md

@@ -0,0 +1,123 @@
+# RequestSender
+
+A simple library for sending HTTP requests.
+
+## Usage
+
+To send a HTTP request.
+
+```js
+import { createRequestSender } from '@bigcommerce/request-sender';
+
+const requestSender = createRequestSender();
+
+// GET request
+requestSender.get('/foobars')
+    .then(({ body }) => console.log(response.body));
+
+// POST request
+requestSender.post('/foobars', { body: { name: 'Foobar' } })
+    .then(({ body }) => console.log(response.body));
+```
+
+To cancel a pending request
+
+```js
+import { createRequestSender, createTimeout } from '@bigcommerce/request-sender';
+
+const timeout = createTimeout(100);
+const requestSender = createRequestSender();
+
+requestSender.get('/foobars', { timeout })
+    .catch(({ status }) => console.log(status));
+
+timeout.cancel();
+```
+
+## API
+
+### createRequestSender()
+
+To create a new instance of `RequestSender`.
+
+### createTimeout(delay: number?)
+
+To create a new instance of `Timeout`. If `delay` is defined, the instance will automatically timeout after the specified period. Otherwise, it remains inactive until `complete()` is called.
+
+### RequestSender
+#### sendRequest(url: string, options: RequestOptions): Promise<Response>
+#### get(url: string, options: RequestOptions): Promise<Response>
+#### post(url: string, options: RequestOptions): Promise<Response>
+#### put(url: string, options: RequestOptions): Promise<Response>
+#### patch(url: string, options: RequestOptions): Promise<Response>
+#### delete(url: string, options: RequestOptions): Promise<Response>
+
+To submit a HTTP request using `GET`, `POST`, `PUT`, `PATCH` or `DELETE` method. Alternatively, you can call `sendRequest` and specify the request method as an argument.
+
+### Timeout
+#### complete(): void;
+
+To manually complete a timeout.
+
+### RequestOptions
+#### body: any?
+Request payload.
+Default: `null`
+
+#### headers: Object?
+Request headers.
+Default: `{
+    'Accept': 'application/json, text/plain, */*',
+    'Content-Type': 'application/json',
+}`
+
+#### params: Object?
+URL parameters. They get serialized as a query string.
+Default: `null`
+
+#### method: string?
+Request method. It's ignored if calling one of the convenience methods (`get`, `post` etc...).
+Default: `GET`
+
+#### credentials: boolean?
+Same as `XMLHttpRequest.withCredentials`.
+Default: `true`
+
+#### timeout: Timeout?
+Define if wish to timeout a request.
+Default: `null`
+
+### Response
+
+#### body: any
+Response body.
+Default: `null`
+
+#### headers: Object
+Response headers.
+Default: `{}`
+
+#### status: number?
+Response status code. Return `0` if the request is cancelled.
+Default: `undefined`
+
+#### statusText: string?
+Response status text.
+Default: `undefined`
+
+## Development
+
+Some useful commands
+
+```sh
+# To test
+yarn test
+
+# To lint
+yarn lint
+
+# To release
+yarn release
+```
+
+For more commands, please see `package.json`