Abandoned Composer Package

Problem/Motivation

The oomphinc/composer-installers-extender package is abandoned, and should be superseded by the drop-in replacement mnsami/composer-custom-directory-installer package.

Steps to reproduce

When running updates via Composer, there is usually a warning to this effect:

Package oomphinc/composer-installers-extender is abandoned, you should avoid using it. No replacement was suggested.

Proposed resolution

Replacing oomphinc/composer-installers-extender with mnsami/composer-custom-directory-installer, as well as adding this package dependency to the composer.json for the module.

Remaining tasks

Updating documentation, particularly installation instructions.

User interface changes

Not applicable.

API changes

Not applicable.

Data model changes

Not applicable.