Should I reveal to a person that my friend has a crush on them?
Why would you want to reveal this?
I've known about it for a while and I'm tired of seeing them suffer.
It isn't your place to do this. Both parties need to decide where their relationship, if one exists, goes.
I don't care. I want to see them get together.
If your friend doesn't want to tell this person about their crush, then I don't think you should either. I think you should respect your friend's wishes and keep that information to yourself.