[rcore] add GetDisplayWidth() and GetDisplayHeight()

src/raylib.h

@@ -999,6 +999,8 @@ RLAPI void SetWindowSize(int width, int height);                  // Set window
 RLAPI void SetWindowOpacity(float opacity);                       // Set window opacity [0.0f..1.0f]
 RLAPI void SetWindowFocused(void);                                // Set window focused
 RLAPI void *GetWindowHandle(void);                                // Get native window handle
+RLAPI int GetDisplayWidth(void);                                  // Get display width
+RLAPI int GetDisplayHeight(void);                                 // Get display height
 RLAPI int GetScreenWidth(void);                                   // Get current screen width
 RLAPI int GetScreenHeight(void);                                  // Get current screen height
 RLAPI int GetRenderWidth(void);                                   // Get current render width (it considers HiDPI)

src/rcore.c

@@ -819,6 +819,18 @@ bool IsWindowState(unsigned int flag)
     return ((CORE.Window.flags & flag) > 0);
 }
 
+// Get display width
+int GetDisplayWidth(void)
+{
+    return CORE.Window.display.width;
+}
+
+// Get display height
+int GetDisplayHeight(void)
+{
+    return CORE.Window.display.height;
+}
+
 // Get current screen width
 int GetScreenWidth(void)
 {