Twitter co-founder Jack Dorsey is stepping down as chief executive of the company.He will be replaced by the current chief technical officer, Parag Agrawal, Twitter said.Mr Dorsey, who co-founded Twitter in 2006, has been serving as CEO of both Twitter and payment firm Square.”It’s finally time for me to leave” he wrote in a statement, saying the company was “ready to move on.”Mr Dorsey said he had “deep” trust in his replacement, and that “I’m deeply grateful for his skill, heart, and soul. It’s his time to lead.”Mr Agrawal joined the firm in 2011, and has been the head of technology since 2017.Mr Dorsey had been under pressure from some investors to step down last year, in favour of a CEO with a single focus