title: ExtJS 4.2.1 - horizontal line of a single value in chart
body: <p>I usually got charts something like this</p>
  
  <p><img src="https://i.stack.imgur.com/6hji1.png" alt="enter image description here"></p>
  
  <p>where i have e.g. for my Target line a complete series.
  This works like a charm.</p>
  
  <p>Though sometimes i have to just compare various things with each other and only got ONE(!) X value. Therefore i also got only one value for my target line and so my series cannot draw the line between points and the result looks like this</p>
  
  <p><img src="https://i.stack.imgur.com/VwIjl.png" alt="enter image description here"></p>
  
  <p>I would need an approach for displaying a horizontal line in this case for my target line. the line should also be shown in the legend. Didnt find anything in the web.</p>