Add ability to indicate the language of styles

[Comandeer]

Type of report

Feature request

Provide description of the new feature

Currently, styles for the "Styles" dropdown are configured via the config.styleSet config variable. However, it could result in a situation when defined styles are in a different language than the rest of the editor's UI. This could pose an issue for screen readers which will read the name of a style with the wrong pronunciation rules.

Due to that, it'd be a good idea to provide an ability to indicate the language of the style name, e.g.:

config.stylesSet = [
    { name: 'Strong Emphasis', language: 'en', element: 'strong' },
    { name: 'Wyróżnienie', language: 'pl', element: 'em' },
    ...
];

This will result in the options in the "Styles" combobox with the appropriate lang attribute.

The alternative approach could allow the translation of the styles names, e.g. by providing the style_<name> entries in the lang files of the stylescombo plugin (see #864).