I know we could all use a good laugh nowadays. But would you settle for a thousand chuckles? Because that’s what “Gutenberg! The Musical!” is offering. In the two-man, 20-character skit of a show that opened Thursday evening on Broadway, the jokes are abundant, interchangeable and lightweight: comedy as packing peanuts. If that suggests an inconsequential payload, well, perhaps consequential was not what the writers, Scott Brown and Anthony King, and the director, Alex Timbers, were after. Silliness crossed with satire seems to be their target, and with the help of two expert farceurs, Josh Gad and Andrew Rannells, they do hit the silliness bull’s-eye. The satire, I’m not so sure.