vale: add DAD as acronym

duplicate address detection (DAD);

- https://en.wikipedia.org/wiki/Neighbor_Discovery_Protocol
- https://datatracker.ietf.org/doc/html/rfc4429

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

_vale/Docker/Acronyms.yml

@@ -25,6 +25,7 @@ exceptions:
   - CSS
   - CSV
   - CVE
+  - DAD
   - DCT
   - DEBUG
   - DHCP