[textures] Image convolution with custom user supplied kernel

[Kimo-s]

Added the function void ImageKernelConvolution(Image *image, float* karnel, int karenlWidth) that does image convolution from a given user kernel defined as 1D array.

Image: Input image
karnel: pointer to1D float array for the kernel
karenlWidth: The width of the kernel matrix

The kernel matrix is only supported for square sized matrices.

Example results:

From left to right: Sharpen kernel, right Sobel operator, Gaussian blur done 6 times, Original image

[raysan5]

I think discussion can follow on open PR, no need for an issue duplicate.