Add Japanese translations

[niw]

Problem

There is no Japanese translations added yet.

Solution

Translate all strings in Japanese.

[1024jp]

Hi, I am just a passing Japanese native macOS app developer.
I have commented on a few points that could be improved.
As for the rest, I think the quality is completely satisfactory.

[niw]

Hi, I am just a passing Japanese native macOS app developer. I have commented on a few points that could be improved. As for the rest, I think the quality is completely satisfactory.

Thank you, updated with your feedbacks!

[maxgoedjen]

Very cool, thank you both!