US President Donald Trump knows the world hangs on his every word. Now he wants you to pay for it. The social media posts of the world’s most powerful man went on sale on Saturday, when his Truth Social business began offering sneak peeks of them to Wall Street traders willing to pay up. The move raises the prospect of big profits for Trump’s company and big questions about insider trading and using public office for private gain. Similar fast speed feeds are sold by other social media firms and...