change regex for email addresses

Frontend/patient_manager/lib/components/inputsAndButtons/mihTextInput.dart

@@ -65,7 +65,8 @@ class _MIHTextFieldState extends State<MIHTextField> {
   }
 
   bool isEmailValid(String email) {
-    return RegExp(r'^[\w-\.]+@[a-zA-Z]+\.[a-zA-Z]{2,}$').hasMatch(email);
+    var regex = RegExp(r'^[a-zA-Z0-9]+@[a-zA-Z.-]+\.[a-zA-Z]{2,}$');
+    return regex.hasMatch(email);
   }
 
   void _onFocusChange() {