New tasks

2. Add Two Numbers/ListNode.cs

@@ -0,0 +1,10 @@
+namespace _2._Add_Two_Numbers;
+
+public class ListNode {
+    public int val;
+    public ListNode? next;
+    public ListNode(int val=0, ListNode? next=null) {
+        this.val = val;
+        this.next = next;
+    }
+}