Add support for setting text part language

[Mgsy]

📝 Provide a description of the new feature

Add support for setting text part language, similar to CKEditor 4 language feature.

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[Mgsy]

Related: #2008

[Reinmar]

Inspiration: https://ckeditor.com/docs/ckeditor4/latest/api/CKEDITOR_config.html#cfg-language_list

[niegowski]

We could simplify configuration by automatically detecting dir like we do it for uiLanguageDirection and contentLanguageDirection: https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/locale.js#L183-L185

[neongreen]

@niegowski

We could simplify configuration by automatically detecting dir

Do you mean that if the user types some text in Hebrew or Arabic, it will automatically be laid out right-to-left even if the rest of the editor content is left-to-right?

Or that the whole editor content will be either right-to-left or left-to-right based whether the majority of the text is in one of the RTL langs or not?

[niegowski]

Do you mean that if the user types some text in Hebrew or Arabic, it will automatically be laid out right-to-left even if the rest of the editor content is left-to-right?

I just meant the language code to "dir" mapping.

[hadifarnoud]

I should be able to change a paragraph's direction as needed. it can detect paragraphs direction based on first percentage of text in LTR or RTL language.

or simply, a LTR/RTL button that allow me to change text direction as needed.