Add support for upcoming packed arrays tags

(originally by neothemachine)

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There is a draft RFC to be published soon which adds support for packed/typed arrays in CBOR, see the [current version](https://tools.ietf.org/html/draft-jroatch-cbor-tags-02). As one of the original CBOR authors is also an author of this proposal I'm sure it will gain widespread adoption in encoders and decoders, especially because it is such a useful feature and will help greatly when big packed arrays need to be efficiently encoded and also decoded both in terms of space usage and speed.

I thought it would be good putting it on the radar for implementation. I think it will be rather straightforward to implement. I currently don't have time for it myself in the next 3-4 weeks but I certainly will help where I can, reviewing code etc.