Load apps/APP/l10n/*.js and themes/THEME/apps/APP/l10n/*.js

[MorrisJobke]

Before it quit right after finding the theme version of the l10n file which results in a not translated part of the UI.

How to reproduce:

• create themes/test/apps/files/l10n/de.js with this:

OC.L10N.register(
	"files",
	{
		"Download" : "Herunterladen2"
	},
	"nplurals=2; plural=(n != 1);"
);

• create themes/test/apps/files/l10n/de.json with this:

{
  "translations": {
    "Download" : "Herunterladen2"
  },
  "pluralForm" :"nplurals=2; plural=(n != 1);"
}

• configure the theme test in config.php
• configure the user to have `Deutsch (Persönlich: Du)" as language
• before: in the files app -> 3 dots menu is not properly translated:

• after: in the files app -> 3 dots menu is properly translated:

I would like to backport this to 13, because it was reported there.

[skjnldsv]

What about custom apps dir?

[MorrisJobke]

What about custom apps dir?

Wasn't included before. And I don't want to mess to bad with this for now. This solved the issues we had for now and we should maybe look into how to make this independent from a theme maybe.