Suggesting additional information to an answer is what comments are for. We accept their use for certain other things, but this is what they are primarily for. The hover text even reads:
Use comments to ask for clarification or add more information. Avoid answering questions in comments.
You might have to do a bit of juggling to add a picture (upload in the answer box and copy the link to the comment), but that would be totally valid. Adding it as an edit is much more awkward, as it already has one graphical representation and your plot is made by a different method.
Or, to make it a full, separate answer
However, you are using a separate method to the other two answers. And I am certainly a big fan of Monte Carlo as a method to analyze complicated dice rolls. It might not be necessary here, but is a useful tool to know about (and it often saves you dealing with all the messy probabilities). So you could expand your answer to be a full answer which explains the method you used. At the moment it is short of that.
A key reminder for whether something should be an answer or a comment to another answer, is whether that solves the problem independently of the other answers. And just a graph doesn't quite do that :)