Using the wikimedia/composer-merge-plugin package is deprecated.

Hi!
I don't see any mention of https://github.com/wikimedia/composer-merge-plugin being outdated. Please feel free to re-open as needed providing more details on which of the usual solutions you would like help with:
- download manually the assets
- use the wikimedia/composer-merge-plugin project
- use oomphinc/composer-installers-extender project
- use npm packagist
etc...