title: Unable to find xmpp.hrl and ejabberd.hrl in ejabberd-19.02
body: <p>I am new with Ejabberd and Erlang and I am trying to add <a href="https://github.com/diamondbybold/ejabberd_mod_offline_post/blob/master/mod_offline_post.erl" rel="nofollow noreferrer">this module</a>. I made the changes like I replace the jlib.hrl with xmpp.hrl and replace the packet by the message as suggested in <a href="https://stackoverflow.com/a/42106413/6544777">this answer</a> my issue is whenever I am trying to compile it say xmpp.hrl and ejabberd.hrl is not found how can I solve this issue.</p>
  
  <p>I want to send the FCM notification to the offline user if some trying to send a message to him. am I doing right? or there have some other best ways to achieve this</p>