Image convolution function ImageKernelConvolution

[Kimo-s]

Please refer to the issue for more info: #3527

[raysan5]

@Kimo-s Thanks for the addition, just added some points to review or further discuss.

Also, as commented on Discord:

I've been thinking about input parameter kernelWidth and I prefer to provide the full length of the array (kernelSize), for security reasons, it would be consistent with other functions that expect an array of values and it can be more easely validated internally if it is square.

For example:

int columns = (int)sqrtf((float)kernelSize);
if (columns*columns != kernelSize)
{
    TRACELOG(LOG_WARNING, "IMAGE: Convolution kernel must be square to be applied");
    return;
}

Another option could be appending zeros if (columns*columns < kernelSize)
But not worries, I can review it after merge

Also, the example window should be 800x450 pixels for consistency with the other examples and web display
the loaded image can be ImageCrop() to 200x450 to fit the 4 images

[raysan5]

@Kimo-s thank you very much for all the reviews! I will merge this new function as soon as raylib 5.0 gets released.

[raysan5]

@Kimo-s thanks for this great addition!