Filters the translations loaded for external TinyMCE 3.x plugins.

The filter takes an associative array (‘plugin_name’ => ‘path’)
where ‘path’ is the include path to the file.

The language file should follow the same format as wp_mce_translation(),
and should define a variable ($strings) that holds all translated strings.

$mce_external_languages = apply_filters( 'mce_external_languages', array(), $editor_id );