Announce Existence of Parent CDS/CSYNC Scanner

In DNS operations, automated scanners are commonly employed by the operator of a parent zone to detect the presence of specific records, such as CDS or CSYNC, in child zones, indicating a desire for delegation updates. However, the presence and periodicity of these scanners are typically implicit and undocumented, leading to inefficiencies and uncertainties. This document proposes an extension to the semantics of the DSYNC resource record, as defined in [RFC9859], allowing parent zones to explicitly signal the presence and scanning interval of such automated scanners. This enhancement aims to improve transparency and coordination between child and parent zones. TO BE REMOVED: This document is being collaborated on in Github at: https://github.com/johanix/draft-berra-dnsop-announce-scanner (https://github.com/johanix/draft-berra-dnsop-announce-scanner). The most recent working version of the document, open issues, etc, should all be available there. The authors (gratefully) accept pull requests.