Fill Gradient Linear
fill-gradient-linear
Sets the linear gradient color when fill-gradient-type=linear is used in conjunction with fit=fill&fill=gradient.
Accepts two values expressed as either color keyword or 3- (RGB) or 6-digit (RRGGBB) hexadecimal color values (fill-gradient-linear=color1,color2).
When fill-gradient-linear is not specified, we will use the color palette of the image and default to vibrant dark for color1 and vibrant light for color2.