What does it do

Use (*json.Encoder).SetZeroizeNilSlice(true) can let the encoder encode nil slice as an empty json array [] instead of null

Why

If we have a nil slive []Type(nil), the encoder will encode it as null. Then the consumers will having trouble with it, they must to check if the field is null first.
A way to solve this problem is always alloc a zero length slice before encoding. However, I want my code be simplify but not fill with make([]Type, 0) every where.

Additional Information

1. This change should be completely backward compatible.
2. The options name is not good, maybe have to decide a better name later.