Added preview image to readme
Added preview image to readme

freakynit/messenger,dieface/messenger,npmcomponent/HubSpot-messenger,giobero999/messenger,leegilon/messenger,rwhitmire/messenger,freakynit/messenger,HubSpot/messenger,HubSpot/messenger,leegilon/messenger,giobero999/messenger,rwhitmire/messenger,npmcomponent/HubSpot-messenger,dieface/messenger