Add docs for configuring a session token.

```php

// Filter S3 Uploads params.

add_filter( 's3_uploads_s3_client_params', function ( $params ) {

	$params['endpoint'] = 'https://your.endpoint.com;

	$params['endpoint'] = 'https://your.endpoint.com';

	$params['use_path_style_endpoint'] = true;

	$params['debug'] = false; // Set to true if uploads are failing.

	return $params;

} );

```

Temporary Session Tokens

=======

If your S3 access is configured to require a temporary session token in addition to the access key and secret, you should configure the credentials using the following code:

```php

// Filter S3 Uploads params.

add_filter( 's3_uploads_s3_client_params', function ( $params ) {

	$params['credentials']['token'] = 'your session token here';

	return $params;

} );

```

Offline Development

=======