used for rv3
copy all the text in lang.json, and create a new file.
paste the text in there.
name the file like "en_US.json"
"en" (english) "US" (United States, try choosing the country where primarily used/area where primarily used)
then, translate all the strings.
be sure to preserve things like %s, %d, etc.
For example, grp.act.account_edit.
"Edit Account (%s)"
Imagine it as if it were like "Edit account (username)".
What would make the most sense?
You can usually view the english version on rv3 itself.