Browns standout Amari Cooper wants more money. And why not? It seems like every other big-name receiver is getting paid more money or is about to be. Cooper skipped OTAs and mandatory minicamp to make his point with Cleveland management. And one of the best cornerbacks in the NFL is throwing support Cooper’s way. Eagles star Darius Slay said this week that Cooper is one of the most “under-appreciated” receivers in the NFL. Surely Slay’s opinion carries some financial heft. “I’m seeing right now that Cleveland don’t want to pay him, they need to pay that man that money,” Slay said on the Green …