Recource Packs Language not working

Language in Recource packs not working

What I expected to happen was...:
A new language was added

What actually happened was...:
It wasn't! It only worked if I put it in assets/lang inside .minecraft.

Steps to Reproduce:
1. Copy-paste a language file.
2. Edit the copy
3. Save it inside your recource pack
4. See the bug.