Previously, shuf exclusively read input from stdin. This PR adds an
option to read from a file using Core::Stream::File. Since a file might
contain arbitrary bytes, including null bytes, this PR represents lines
as Spans of Bytes instead of Strings.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
