Potential spec changes

[makew0rld]

• Decoders coerce undefined into null, see Fix undefined invalid_out #4
  • This is only necessary if you want to support historical dag-cbor objects, see here
  • Filed upstream: DRISL: undefined darobin/dasl.ing#51
• Make the empty CID invalid
  • See this Bluesky thread
  • Also filed upstream: Specify that hash length should be correct darobin/dasl.ing#45
  • Personally I think this is valid and a quirk of hash length representing truncation
• Reduce integer range, cf Integer range constraints darobin/dasl.ing#29
  • This makes designing libs and APIs easier, especially in Go
  • Would encoding/decoding integers beyond that range be an error? This would invalidate a bunch of existing libs
  • Should the range be reduced to int64 or JavaScript safe int range? (I would say the former)