Maintenance and review of Drupal core COPYRIGHT.txt

Problem/Motivation

There is no guidance for maintaining the core COPYRIGHT.txt. Every major release the JavaScript section is updated which is a tedious, boring and repeats information available in the JavaScript library code.

Steps to reproduce

Proposed resolution

Add a paragraph that covers JavaScript similar to what is done for PHP assets.
Create some docs in the core committer handbook for how to maintain this file.

Remaining tasks

User interface changes

API changes

Data model changes