Add guidance links

[Sakurann]

It feels like there are different types of work being mixed under the same label.

• there is no concrete guidance from OWF yet, so probably better to label that under "relevant organizations" category or something.
• ESI url is a guidance how to do JaDES, I was confused why it was considered guidance for the wallet.
• for SVIP, better to link to a DHS url than an email archive

Would also be good to clarify that listed "guidance on wallets" all cover different scopes (for example EUDIW covers transport protocol that DHS does not, while DHS covers cryptosuites while EUDIW does not)

[OR13]

for SVIP, better to link to a DHS url than an email archive

Best I can do for now, the links might change in the future.

Would also be good to clarify that listed "guidance on wallets" all cover different scopes (for example EUDIW covers transport protocol that DHS does not, while DHS covers cryptosuites while EUDIW does not)

This is interesting, having the references all in one place does allow us to compare / summarize similarities and differences, but I am not sure I am prepared to do that in this PR.... it does seem like a valuable thing to do.