Extend documentation regarding disabling of installers

Please extend [the documentation regarding disabling of certain installers](https://github.com/composer/installers/blob/2a9170263fcd9cc4fd0b50917293c21d6c1a5bfe/README.md?plain=1#L248).

My first thought was that you have to list [types](https://github.com/composer/installers/blob/2a9170263fcd9cc4fd0b50917293c21d6c1a5bfe/README.md?plain=1#L39), i.e. `wordpress-plugin`, which does not work. My next thought was that you have to list [the filename of an Installer](https://github.com/composer/installers/tree/2a9170263fcd9cc4fd0b50917293c21d6c1a5bfe/src/Composer/Installers), i.e. `WordPressInstaller`, which also does not work.

Only after searching the code where this is actually [implemented](https://github.com/composer/installers/blob/2a9170263fcd9cc4fd0b50917293c21d6c1a5bfe/src/Composer/Installers/Installer.php#L247) and going backwards from there I found the [array keys which I can use](https://github.com/composer/installers/blob/2a9170263fcd9cc4fd0b50917293c21d6c1a5bfe/src/Composer/Installers/Installer.php#L22). This seems a bit too much search work to me.

A table of the possible values would be really helpful at this point of the documentation; just like above with the available types.