docs: add more sample code

Author: kenjis

user_guide_src/source/libraries/time/001.php

@@ -2,5 +2,7 @@
 
 use CodeIgniter\I18n\Time;
 
-$myTime = new Time('+3 week');
+$myTime = new Time('2024-01-01');
+$myTime = new Time('2024-01-01 12:00:00');
 $myTime = new Time('now');
+$myTime = new Time('+3 week');