Add a "user languages" folder for translations

[Adrian2k7]

Hello,

Actual state

There are currently 2? official locations for translations.

• Folder within plugin/theme
• Folder wp-content/languags

The problem with these two is,

• that both are managed automatically and users are not able to edit them, without risking loosing translations.
• A plugin is needed for just a few translations
• Plugins can't work together on the same language base

Suggestions

Introduce an additional language folder, the user can put custom translations files into, which are not removed by updates ...
I.e.

wp-content/languages/custom

This would also be nice, as plugins may all use this folder and allow some kind of interoperability:

• i.e. the basic user could use Loco Translate, but the power user could use PoEdit to edit the same files
• an upgrade from Loco Translate to i.e. a multilingual site with WPML might be easier

[SergeyBiryukov]

Previously: #17266, #28571.