isFocused method added (#1833)

Co-authored-by: Ethan Sharabi <[email protected]>

Author: avishain

demo/src/screens/MainScreen.js

@@ -103,7 +103,7 @@ class MainScreen extends Component {
   };
 
   closeSearchBox = () => {
-    this.input.blur();
+    this.input?.blur();
   };
 
   setDefaultScreen = item => {

src/incubator/TextField/useImperativeInputHandle.ts

@@ -7,6 +7,7 @@ const useImperativeInputHandle = (ref: React.Ref<any>, props: Pick<TextInputProp
   const context = useContext(FieldContext);
   useImperativeHandle(ref, () => {
     return {
+      isFocused: () => inputRef.current?.isFocused(),
       focus: () => inputRef.current?.focus(),
       blur: () => inputRef.current?.blur(),
       clear: () => {