title: Format List View in JSON - row borders? My own styles?
body: <p>I have a list view in SharePoint Online that I'm formatting using JSON. I'm trying to set it so the rows have top borders (ideally, I'd like it to be conditional, but let's walk before we run). </p>
  
  <p>I don't want to do anything else. There are a lot of columns, so I don't want to create a child for each field if I can avoid it. Besides, I don't think that will do what I want. </p>
  
  <p>I've done lots of looking around (including the examples in GitHub, UI Fabric) and it appears that the only way to format a row in a view is to apply a class, and the only classes I can find that seem to be available are the built in ones like sp-field-severity--good. I couldn't find any that just had a top border.</p>
  
  <p>So my questions are these:
  - is there a comprehensive list of these classes somewhere? 
  - can I set a CSS style on a row or create my own CSS class to apply?</p>