Jem Aswad Senior Music EditorAt 18, first-time voter Billie Eilish is the youngest music artist to appear at the Democratic National Convention, and she made the most of the platform, delivering a strong speech against President Donald Trump, advocating Joe Biden and imploring Americans to vote.She was introduced by host Kerry Washington, who spoke of the voter-registration booths at Eilish’s concerts — which were present before the singer was old enough to vote — and her efforts to reduce the