Alternative tags have now been standardised

[dcoutts]

We should add support.

https://datatracker.ietf.org/doc/html/draft-bormann-cbor-notable-tags#section-9
https://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml

     +============+=============+===================================+
     |       Tags | Data Item   | Meaning                           |
     +============+=============+===================================+
     |   121..127 | any         | alternatives 0..6, 1+1 encoding   |
     +------------+-------------+-----------------------------------+
     | 1280..1400 | any         | alternatives 7..127, 1+2 encoding |
     +------------+-------------+-----------------------------------+
     |        101 | array       | alternatives as given by the uint |
     |            | [uint, any] | + 128                             |
     +------------+-------------+-----------------------------------+

           Table 13: Tags for Enumerated Alternative Data Items