title: Wordpress adding custom fields into post's front end
body: <p>i want to make a wordpress plugin that will display some content at the end of each post. let's say for example 'Hello world'.
  But looking at the wordpress API, i don't find any relevant indications about how to do this.</p>
  
  <p>i don't want a widget, but only a plugin that does only that: displays me a static text at the end of every article. </p>
  
  <p>any idea about how this should be done?</p>
  
  <p>thanks!</p>