added 3 screen mod to login

lib/core/utils/display_size_detector.dart

@@ -0,0 +1,35 @@
+import 'package:flutter/material.dart';
+
+enum DisplaySize {
+  extraSmall, //mobile
+  small, //tablet
+  medium, //laptop
+  large, //desktop
+}
+
+extension DisplaySizeDetector on Size {
+  DisplaySize get displaySize {
+    if (width < 600) {
+      return DisplaySize.extraSmall;
+    } else if (width < 1024) {
+      return DisplaySize.small;
+    } else if (width < 1440) {
+      return DisplaySize.medium;
+    } else {
+      return DisplaySize.large;
+    }
+  }
+
+  String get displaySizeName {
+    switch (displaySize) {
+      case DisplaySize.extraSmall:
+        return 'Mobile';
+      case DisplaySize.small:
+        return 'Tablet';
+      case DisplaySize.medium:
+        return 'Laptop';
+      case DisplaySize.large:
+        return 'Desktop';
+    }
+  }
+}