There is no way to upvote an editor of a post in a way that would give them points or anything like that. It is also better not to think of upvoting as upvoting the user that wrote the post, but rather as upvoting the post. Thus, if you like the post now, upvote the post.
I'd rather advise against upvoting an other post of the editor or things like that.
What you can do is write a comment addressed at the editor that positively acknowledges their work. It is better not do this systematically but in exceptional cases I think it is fine:
@{editing user's name}: thank you for clarifying this post, I saw its original version and did not understand it. Now, it is very clear and interesting.
Note that one can actually comment-notify editors, even though auto-complete does not propose them.
Since you tagged this feature request let me add that I do not think such a feature is needed or desirable. I feel there is some value in edits being just altruistic as far as points go.