Added destroy method

src/lib/components/tests/Keyboard.test.js

@@ -1222,4 +1222,14 @@ it('Keyboard inputName change will trigget caretPosition reset', () => {
   keyboard.getButtonElement("b").onpointerdown();
 
   expect(keyboard.caretPosition).toBe(null);
+});
+
+it('Keyboard destroy will work', () => {
+  testUtil.setDOM();
+
+  let keyboard = new Keyboard();
+
+  keyboard.destroy();
+
+  expect(keyboard.keyboardDOM.innerHTML).toBeFalsy();
 });