Implement optional serde feature

[bassmanitram]

This is part of a larger effort to try and find a way to introspect simd_json Deserializer Tapes before actually deserializing. Since it's not actually possible to get at the tape in a serde::Deserialize::deserialize function, the next best thing is (possibly) to recreate the tape from the deserializer using standard deserialization - a kind of pass-thru. This will surely not perform TOO well, but it's really no different from serde_json's own RawValue deserialization. Anyway, in make Node deserializable in in simd_json, we need to, be able to deserialize StaticNode from here - hence the PR.

The above approach has the "advantage" of being able to deserialize anything into a Tape - not sure that's of any use actually.

This related to simd-lite/simd-json#366

[Licenser]

the 0.14. rc's have a lazy value that allows to keep a tape until it's mutated, I couldn't get it to be fully value-trait compatible but it's workabkle