By Narottam Medhora and Rishika Sadam, Reuters June 21 (Reuters) – Twitter, known for its 140-character limit on tweets, is now allowing users to post longer videos – of up to 140 seconds. The change highlights co-founder Jack Dorsey-led Twitter’s recent push into video, an area where it lags Facebook and Google’s YouTube, and efforts to revive stalled user growth. In another move, Twitter will start allowing video publishers to make money out of their content on Vine, its video streaming service. Vine will use Twitter’s Amplify Open program, which runs ads before a video starts playing. Twitter previously restricted videos to 30 seconds. The new 140-second video limit also applies to Vine, which previously had a six-second limit. Twitter also launched “Twitter Engage”, a mobile app that allows users with a large number of followers to track their posts and see what their fans are tweeting about. “It is [...]