Skip empty 0's in hexdump

[wcampbell0x2a]

As hexyl does, skip columns of 0x00s.

│00000390│ 00 00 00 00 00 00 00 00 ┊ 00 00 00 00 00 00 00 00 │⋄⋄⋄⋄⋄⋄⋄⋄┊⋄⋄⋄⋄⋄⋄⋄⋄│
│*       │                         ┊                         │        ┊        │
│00001010│ 00 00 00 00 00 00 00 00 ┊ 01 03 00 00 00 00 00 00 │⋄⋄⋄⋄⋄⋄⋄⋄┊••⋄⋄⋄⋄⋄⋄│