Update useBackHandler.js

Every time this function was called you will add a new `addEventListener`, now we passed an argument to create a new listener only when receive a new function

Author: ronal2do

lib/useBackHandler.js

@@ -1,12 +1,14 @@
-import React, { useEffect } from 'react'
+import { useEffect} from 'react'
 import { BackHandler } from 'react-native'
 
-export default function useBackHandler(handler) {
+export default function useBackHandler(handler: () => boolean) {
   useEffect(() => {
     BackHandler.addEventListener('hardwareBackPress', handler)
-
     return () => {
-      BackHandler.removeEventListener('hardwareBackPress', handler)
-    }
-  })
+      BackHandler.removeEventListener(
+        'hardwareBackPress',
+        handler
+      );
+    };
+  }, [ handler ])
 }