WASHINGTON (Reuters) – U.S. President Joe Biden signed a new weapons package worth up to $400 million for Ukraine on Friday, including four additional high mobility artillery rocket systems (HIMARS) and more ammunition. The new U.S. aid is meant to bolster Ukraine as it confronts heavy pounding by Russian artillery. Since the Feb. 24 invasion, Russian forces have taken control of a big chunk of territory across Ukraine’s southern flank above Crimea, which Russia annexed in 2014. Russia is slowly pushing Ukrainian forces out of two Russian-backed rebel regions of east Ukraine which it has recog…