Add onValueChanged function for component

[andrewtelnov]

onValueChanged function will allow to avoid using question.valueChangedCallback callback. Here is the small example:

Survey.ComponentCollection.Instance.add({
    name: "dropdown_and_text",
    elementsJSON: [
      {
        type: "dropdown",
        name: "combo",
        choices: ["A", "B", "C"],
      },
      { type: "text", name: "text1" },
      { type: "text", name: "text2" },
    ],
    onValueChanged: (question, name, value) => {
     //If combo is changed, then set a double value of "combo" to "text1" and clear "text2"
      if (name == "combo") {
        question.setValue("text1", value + value);
        question.setValue("text2", null);
      }
    },
  });