auro-icon: Include warning info about CDN in README

[blackfalcon]

General Support Request

The auro-icon README should be updated to include specific information regarding the use of a public CDN call that may become unstable and the Auro team is not able to directly support a solution.

Possible Solution

Add a new section to the README that clearly states that the default setup of auro-icon is using a public FREE CDN solution and alerts the user as to the risks of this in critical production applications.

This content should also include information about the url attribute of the API that allows users to point to an alternate CDN endpoint as needed.

Additional context

n/a