Add implicit operator constructor to PhoneNumber type

Author: codejudas

src/Twilio/Types/PhoneNumber.cs

@@ -16,6 +16,16 @@ public PhoneNumber(string number)
             _number = number;
         }
 
+        /// <summary>
+        /// Add implicit constructor for PhoneNumber to make it assignable from string
+        /// </summary>
+        /// <param name="number">Phone number</param>
+        /// <returns></returns>
+        public static implicit operator PhoneNumber(string number)
+        {
+            return new PhoneNumber(number);
+        }
+
         /// <summary>
         /// Convert to string
         /// </summary>