The Link HTTP header can do the same as link elements,
in that they can preload/prefetch/etc... This implements
the basics of header parsing and hooks it up for preload.
Note that we use a new nom-rfc8288 crate that implements
the parsing behavior. However, that crate is too strict
in that empty attributes (;; as part of the header) are
discarded and resulting in a parsing failure. Therefore,
we use its lenient parsing mode.
Part of #35035
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Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
Signed-off-by: Tim van der Lippe <TimvdLippe@users.noreply.github.com>
Co-authored-by: Josh Matthews <josh@joshmatthews.net>
