If a girl touches you on the shoulder and the arms is that a good sign they like you?

Just recently a girl who I've been friends with for a while has started to think all my jokes are hysterically funny and today i just randomly told her something that she agreed with and said "I KNOW!" and put her hand on my shoulder for a split second and took it off. I'm afraid that she might have figured out that l like her (even though I haven't told anybody) just based on the way I act around her, so do you think that she likes me for real, is just being friendly or is just messing with me?