Cliff Sims, the founder and CEO of Birmingham-based Yellowhammer Multimedia, will be part of President-elect Donald Trump's administration. Sims, who joined the Trump campaign in 2016, will serve as assistant communications director for White House message strategy and special assistant to the president, according to a release. With Sims taking a role in the White House, he will resign as CEO of Yellowhammer on Friday. Brian Ellis, chief business development officer for Yellowhammer, has been…