Add ability to translate language names in the language plugin

[Comandeer]

Type of report

Feature request

Provide description of the new feature

At the moment the default list of languages is hardcoded right inside the plugin →

ckeditor4/plugins/language/plugin.js

Line 26 in 0150a16

var languagesConfigStrings = ( editor.config.language_list || [ 'ar:Arabic:rtl', 'fr:French', 'es:Spanish' ] ),

However, the fact that all languages are defined by the ISO-639-1 codes means that it should be possible to provide translations for their names (Library of Congress provides translations for English, French and German) in the plugin's lang files. It should be even possible to simplify the format of the config.language_list configuration variable from <languageCode>:<languageLabel>[:<textDirection>] to <languageCode>[:<textDirection>].