Multilingual support for Multiselect Dropdown

Problem/Motivation

First of all, thanks for creating and maintaining this module!

Correct me if I'm wrong, but could it be that the module doesn't support multilingual out of the box.
I looked into the Configuration translation on the view and the User interface translation, but none of my labels could be found. For example:

label-none
label-single
label-plural
label-all
etc.

I used the BEF multiselect dropdown module on a views page.

Steps to reproduce

Add facets 3.0 to views filters and expose them.
Use BEF as exposed form style.
Set Exposed filter widget to Multiselect Dropdown
Change some labels
Try to translate the labels

Thanks in advance for having a look or showing me how to translate the labels!