Add a Pure Black Theme

[ygxxii]

The Dark Theme is pretty good.Would you please add a pure black theme?

Cause the pure black theme perfoms better on OLED devices.

[ThirtyDegreesRay]

I already know what you mean, but I don't have OLED devices, so I will try some way to perfoms better on OLED devices, but I can't see it directly, cloud you tell me the perfoms on OLED devices when pure black theme added.