[cv2] cv2.add can accept scalar value, not only `Mat`

[xnuk]

Currently defined as def add(src1: Mat, src2: Mat, ...):

python-type-stubs/cv2/__init__.pyi

Line 1697 in dd9e65c

def add(src1: Mat, src2: Mat, dts: Mat = ..., mask: Mat = ..., dtype=...) -> typing.Any:

But both src1 and src2 can be a scalar value, according to OpenCV documents:

Parameters

• src1 first input array or a scalar.
• src2 second input array or a scalar.

from: https://docs.opencv.org/4.6.0/d2/de8/group__core__array.html#ga10ac1bfb180e2cfda1701d06c24fdbd6