mark 'force' as optional property of PressEvent object (#29006)

Summary:
Refs:
* https://github.com/facebook/react-native/blob/master/React/Fabric/RCTSurfaceTouchHandler.mm#L93
* https://github.com/facebook/react-native/blob/master/RNTester/js/examples/Pressable/PressableExample.js#L25

According to the current implementation `force` will be returned only on `iOS` platform, only on the devices which have a hardware 3D touch capabilities.

## Changelog

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[General] [Fixed] - mark `force` as an optional property of the PressEvent object
Pull Request resolved: #29006

Test Plan: Go CI!

Reviewed By: cpojer

Differential Revision: D21797241

Pulled By: TheSavior

fbshipit-source-id: e66be6958a2251bc8585e87e6bad54484a067949

Libraries/Types/CoreEventTypes.js

@@ -88,7 +88,7 @@ export type TextLayoutEvent = SyntheticEvent<
 export type PressEvent = ResponderSyntheticEvent<
   $ReadOnly<{|
     changedTouches: $ReadOnlyArray<$PropertyType<PressEvent, 'nativeEvent'>>,
-    force: number,
+    force?: number,
     identifier: number,
     locationX: number,
     locationY: number,

RNTester/js/examples/Pressable/PressableExample.js

@@ -167,7 +167,7 @@ function ForceTouchExample() {
           style={styles.wrapper}
           testID="pressable_3dtouch_button"
           onStartShouldSetResponder={() => true}
-          onResponderMove={event => setForce(event.nativeEvent.force)}
+          onResponderMove={event => setForce(event.nativeEvent?.force || 1)}
           onResponderRelease={event => setForce(0)}>
           <Text style={styles.button}>Press Me</Text>
         </View>