title: how to add read more button on wordpress post without inserting any read more tag
body: <p>I want to add read more button after 70 or 100 words. if any special case will occur in this word interval it will be considered. ie:
  after 65 word read more text while creating post. Any idea? I am apologizing if I am requesting a very novice type help. I am new wordpress. Thanks in advance.  </p>