fix: calculate header size for offeset column

[Its-Just-Nans]

The size of the offset column is hardcoded

This break the output with large files (eg 4 Go)

cargo run -- --skip 4928310100 --length 20 larg_file.ext

BEFORE

┌────────┬─────────────────────────┬─────────────────────────┬────────┬────────┐
│0125c00b54│ 00 00 00 00 00 00 00 00 ┊ 00 00 00 00 00 a0 04 c0 │⋄⋄⋄⋄⋄⋄⋄⋄┊⋄⋄⋄⋄⋄ו×│
│0125c00b64│ 25 01 00 00             ┊                         │%•⋄⋄    ┊        │
└────────┴─────────────────────────┴─────────────────────────┴────────┴────────┘

AFTER

┌──────────┬─────────────────────────┬─────────────────────────┬────────┬────────┐
│0125c00b54│ 00 00 00 00 00 00 00 00 ┊ 00 00 00 00 00 a0 04 c0 │⋄⋄⋄⋄⋄⋄⋄⋄┊⋄⋄⋄⋄⋄ו×│
│0125c00b64│ 25 01 00 00             ┊                         │%•⋄⋄    ┊        │
└──────────┴─────────────────────────┴─────────────────────────┴────────┴────────┘

[Its-Just-Nans]

The CI macos-13 is not usable anymore

fixed in #256