Added sign up screen and model

lib/features/auth/model/signup_model.dart

@@ -0,0 +1,29 @@
+class SignUpModel {
+  final String email;
+  final String password;
+  final String firstName;
+  final String lastName;
+
+  SignUpModel(
+      {required this.email,
+      required this.password,
+      required this.firstName,
+      required this.lastName});
+
+  factory SignUpModel.fromJson(Map<String, dynamic> json) {
+    return SignUpModel(
+        email: json['email'],
+        password: json['password'],
+        firstName: json['firstName'],
+        lastName: json['lastName']);
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'email': email,
+      'password': password,
+      'firstName': firstName,
+      'lastName': lastName,
+    };
+  }
+}