Eileen Wang, the mayor of Arcadia, Calif., resigned on Monday after federal prosecutors announced they had charged her with acting as an illegal agent of the Chinese government. She will plead guilty to the charge, according to a plea deal unsealed the same day. The felony charge comes with a potential sentence of up to 10 years in prison. The court document outlined Ms. Wang’s efforts, beginning in late 2020 and continuing until at least the end of 2022, to operate a purported news website called U.S. News Center that…