Enhances example in README with import statement.

Author: Martin Wentzel

README.md

@@ -24,6 +24,8 @@ $ yarn add node-ssh-forward
 Setting up the initial ssh connection (using a bastion host)
 
 ```js
+import { SSHConnection } from ‘node-ssh-forward’
+
 const sshConnection = new SSHConnection({
   endHost: 'example.com',
   bastionHost: 'my-bastion-host.com'