Retaining the modified title on component unmount made optional. (#2)

* Option added to retain the modified title or to rollback to the default title ON the corresponding component unmount event (e.g. route change -> title change for those using this hook, but rollback to the default/original title for those routes not using this hook.)

* Using useRef to get the default title.

Author: kckusal

index.js

@@ -1,10 +1,16 @@
 'use strict';
-let { useEffect } = require('react');
+let { useRef, useEffect } = require('react');
+
+function useDocumentTitle(title, retainOnUnmount = false) {
+  const defaultTitle = useRef(document.title);
 
-function useDocumentTitle(title) {
   useEffect(() => {
     document.title = title;
-  }, [title])
+
+    return () => {
+      if (!retainOnUnmount) document.title = defaultTitle.current;
+    };
+  }, [title]);
 }
 
 module.exports = useDocumentTitle;