Create a composer.libraries.json file

As per #3

You need to composer require wikimedia/composer-merge-plugin

and add the following to the site's composer.json:

        "merge-plugin": {
            "include": [
                "[docroot]/modules/contrib/ckwordcount/composer.libraries.json"
            ]
        },

Where [docroot] is your site's root (web/docroot).

Sorry @hchonov, but the previous composer.json dependency never worked correctly, so it's not a real BC-break. See #3172165: Composer setup does not install the plugin in the libraries folder

It only worked if you used the mnsami/composer-custom-directory-installer plugin and had prepared the composer.json like in the previous instructions. And yes, I do realize a few select sites might be in that situation. The solution for those is to fix those site's composer.json. Reverting is not an option.

I've created a 1.4 release that re-introduces the dependency on w8tcha/ckeditor-wordcount-plugin

OK. So version 1.4 is even worse as it triggers a problem in one of the composer plugins (not sure if mnsami/composer-custom-directory-installer, or oomphinc/composer-installers-extender or wikimedia/composer-merge-plugin), that results in the library not being installed.

At this point, I don't think that it is possible to keep the composer.libraries.json in the 1.x branch. I'll create a 1.5 release that removes it, and
then a 2.0 release that uses it and will be almost exactly the same as version 1.3.

Sorry about this mess everyone.