Provide a proper integration with Libaries API

Problem

The current implementation is not integrating with the Libraries API → . This makes it hard to

• Include a self-hosted library into the default JS aggregation behavior.
• Define an externally hosted library to be loaded asynchronously (i.e. using the async attribute - btw this is also not the case currently).
• Individually alter the library for adding or removing further attributes / inclusion weights.

Proposed solution

Integrate with the Libraries API.