Converse i18n - Date Format

Converse does not properly set the date format based on the i18n parameter.

https://github.com/conversejs/converse.js/blob/master/src/converse-chatview.js#L555-L558

It use dayjs to always set the date as day_date.format("dddd MMM Do YYYY"), resulting in a mardi mai 5 2020 in french instead of a mardi 5 mai 2020.