Proper way to package translation files with a custom module? I have a custom module. In this module all strings are in English. However, my website is in French and when installing the custom module, I'd like the French strings to be picked up and imported automatically.

What's the best way to generate and then package the .fr.po translation file with my custom module?

(With D7, I would use potx to generate the .po file for my module, then I'd put the file under sites/all/modules/custom/MYMODULE/translations. But potx no longer exists for D8 and the d.org documentation isn't very helpful.)
potx itself isn't directly available as a Drupal 8 module, but it doesn't need to.

It also works as a drush extension and can be run on Drupal 8 code. Haven't tried it if providing a translations folder still works, but I think so.

So, still works pretty much the same as in Drupal 7.