Add a Whatsapp block that includes the chatwithio javascript

Problem/Motivation

We need to create a block plugin that renders the javascript file provided by chatwithio. This script needs to be included as part of a library, additionally the ID of the user/account needs to be configurable.

Proposed resolution

The solution must include:

• A configuration form rendered somewhere in admin/config/webservices or similar.
• A library that loads up the external javascript file
• A block plugin that uses this configuration and renders the library which ends up showing the whatsapp widget.