It doesn't get much better than this for the Los Angeles Chargers : Signing tight end David Njoku in free agency provides a boost to Justin Herbert’s offense, no doubt.  But double exclamation points here: It also gives the Chargers an incredible veteran mentor for breakout second-year tight end Oronde Gadsden.  The Chargers and Njoku agreed to terms on a one-year deal worth up to $8 million Monday, according to NFL Network’s Ian Rapoport . That’s one week after the former Cleveland Browns star’s  reported visit to the Chargers .  At the time, we broke down why Njoku was a good fit for Mike McDaniel’s offense and the impact it would have on Gadsden.  Now, it’s official.  Chargers sign David Njoku: Impact on Oronde Gadsden David Njoku | Ken Blaze-Imagn Images Turning 30 in July, Njoku has seen it all in the NFL since entering the league in 2017 via the first round.  No hyperbole: Njoku’s number of quarterbacks who have thrown him a pass has almost surpassed his age.…