Add section explaining the two different urls for the final spec

Author: jogu

openid-4-verifiable-presentations-1_0.md

@@ -73,6 +73,10 @@ Additionally, it defines how to use OpenID4VP in conjunction with the Digital Cr
 * Tobias Looker (MATTR)
 * Adam Lemmon (MATTR)
 
+## Errata revisions
+
+The latest revision of this specification, incorporating any errata updates, is published at [openid-4-verifiable-presentations-1_0](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html). The exact text you are currently looking at will always be available at [openid-4-verifiable-presentations-1_0-final](https://openid.net/specs/openid-4-verifiable-presentations-1_0-final.html). When referring to this specification from otber documents, it is recommended to reference [openid-4-verifiable-presentations-1_0](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html).
+
 ## Requirements Notation and Conventions
 
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [@!RFC2119] [@!RFC8174] when, and only when, they appear in all capitals, as shown here.