Include codepage in LanguageConfiguration.json for each language

[axtens]

E.g. Hangul's is https://en.wikipedia.org/wiki/Code_page_949_(IBM)

[axtens]

The include it in RTF header

[axtens]

Maybe store everything in either \userprops or \info. Userprops works as below

{\info}
{\*\userprops
    {
        {\propname HTML}
        \proptype11
        {\staticval 1}
    }
    {
        {\propname DocumentEncoding}
        \proptype30
        {\staticval utf-8}
    }
}