Add GS1 to the implementation status section

[dret]

probably addressed by https://github.com/dret/I-D/commit/a60b02b8a6a1a895d2cf90cab8f4c0861b110b23

[philarcher]

I'm happy to confirm that GS1 is happy with that text, thank you.

[hvdsomp]

added to the I-D

[philarcher]

We're making progress with our implementation. By the end of this month expect to see:

• The next iteration of the GS1 Digital Link standard in public review. It will say that its inclusion of Linkset is informative but only until such time as Linkset becomes an RFC when the citation will be normative. The text of the GS1 standard itself shouldn't need to change.
• We're already making progress with actual implementation and addition of our use of Linkset included in our resolver test suite.

More soon...