Can't override translation of JSCalendar in Jira for Ukrainian language pack

I take a part of making Ukrainian language pack for Jira.
All Jira i18n keys stored in *.properties files. JSCalendar is a 3rdparty library that uses for displaying calendar near DatePickers.
Translation files for this calendar STORED IN THIS MODULE and my team cannot change anything or override translation.

The library is abandoned since 2005.

I found tutorial how to translate this calendar
but this manual requires change files inside my jira_home directory.
I don’t know how can I add webresource with my translated calendars file and make to work it.
Please, help