Replaced GenImageGradientH and GenImageGradientV with GenImageLinearGradient (#3074)

* Replaced GenImageGradientH and GenImageGradientV with GenImageLinearGradient

* renamed GenImageLinearGradient to GenImageGradientLinear

src/raylib.h

@@ -1239,8 +1239,7 @@ RLAPI bool ExportImageAsCode(Image image, const char *fileName);
 
 // Image generation functions
 RLAPI Image GenImageColor(int width, int height, Color color);                                           // Generate image: plain color
-RLAPI Image GenImageGradientV(int width, int height, Color top, Color bottom);                           // Generate image: vertical gradient
-RLAPI Image GenImageGradientH(int width, int height, Color left, Color right);                           // Generate image: horizontal gradient
+RLAPI Image GenImageGradientLinear(int width, int height, int direction, Color start, Color end);        // Generate image: linear gradient
 RLAPI Image GenImageGradientRadial(int width, int height, float density, Color inner, Color outer);      // Generate image: radial gradient
 RLAPI Image GenImageChecked(int width, int height, int checksX, int checksY, Color col1, Color col2);    // Generate image: checked
 RLAPI Image GenImageWhiteNoise(int width, int height, float factor);                                     // Generate image: white noise