fix(registry): resolve empty standard URL for CMEA (TIA TR45.0.A)

[Mehrn0ush]

Summary

The CMEA entry has an empty standard.url field, which makes the reference non-actionable.

Location

schema/cryptography-defs.json
family: "CMEA"
standard.name: "TIA TR45.0.A"
standard.url: "" (empty)

Questions / Proposed resolution

• Should registry entries allow empty URL values, or should URL always be a resolvable reference?
• If the standard is paywalled, is linking to an official purchase/procurement page acceptable?

Notes

INCITS describes official procurement channels for standards via ANSI/Techstreet.

[stevespringett]

Should registry entries allow empty URL values, or should URL always be a resolvable reference?

Ideally, no.

If the standard is paywalled, is linking to an official purchase/procurement page acceptable?

Yes

[bhess]

Usually a patent is referenced for CMEA: https://patents.google.com/patent/US5159634
Added this in PR #844