Snake: Add snake color chooser game menu action

This patch makes use of a new "set_snake_base_color()" function to
change the snake's base color to the picked value.

Userland/Games/Snake/SnakeGame.h

@@ -22,6 +22,8 @@ public:
     void pause();
     void reset();
 
+    void set_snake_base_color(Color color) { m_snake_base_color = color; };
+
 private:
     explicit SnakeGame(NonnullRefPtrVector<Gfx::Bitmap> food_bitmaps);