Update whats_new.rst for 1.8.18 release. (#1568)

* Update whats_new.rst for 1.8.18 release.

* Update PR number

* Add missing PR.

docs/about/whats_new.rst

@@ -7,6 +7,10 @@ What's New
 
 v1.8.next
 =========
+
+v1.8.18 (27th March 2024)
+=========================
+
 - Add dataset cli tool ``find-duplicates`` to identify duplicate indexed datasets (:pull:`1517`)
 - Make solar_day() timezone aware (:pull:`1521`)
 - Warn if non-eo3 dataset has eo3 metadata type (:pull:`1523`)
@@ -17,9 +21,11 @@ v1.8.next
 - Add new ODC Cheatsheet reference doc to Data Access & Analysis documentation page (:pull:`1543`)
 - Compatibility fix to allow users to supply ``odc.geo``-style GeoBoxes to ``dc.load(like=...)`` (:pull:`1551`)
 - Fix broken codecov github action. (:pull:`1554`)
+- Update documentation links to DEA Knowledge Hub (:pull:`1559`)
 - Throw error if ``time`` dimension is provided as an int or float to Query construction
   instead of assuming it to be seconds since epoch (:pull:`1561`)
 - Add generic NOT operator and for ODC queries and ``Not`` type wrapper (:pull:`1563`)
+- Update whats_new.rst for release (:pull:`1568`)
 
 v1.8.17 (8th November 2023)
 ===========================