Update whatsnew for v3.3.0rc0 (#4921)

* update whatsnew

* fix index

* remove template

* address review comments

docs/src/whatsnew/latest.rst → docs/src/whatsnew/3.3.rst

@@ -1,13 +1,13 @@
 .. include:: ../common_links.inc
 
-|iris_version| |build_date| [unreleased]
-****************************************
+v3.3 (18 Aug 2022) [release candidate]
+**************************************
 
 This document explains the changes made to Iris for this release
 (:doc:`View all changes <index>`.)
 
 
-.. dropdown:: :opticon:`report` |iris_version| Release Highlights
+.. dropdown:: :opticon:`report` v3.3.0 Release Highlights
  :container: + shadow
  :title: text-primary text-center font-weight-bold
  :body: bg-light
@@ -16,7 +16,16 @@ This document explains the changes made to Iris for this release
 
  The highlights for this minor release of Iris include:
 
- * N/A
+ * We've added support for datums, loading them from NetCDF when the
+ :obj:`iris.FUTURE.datum_support` flag is set.
+ * We've greatly improved the speed of linear interpolation.
+ * We've added the function :func:`iris.pandas.as_cubes` for richer
+ conversion from Pandas.
+ * We've improved the functionality of :func:`iris.util.mask_cube`.
+ * We've improved the functionality and performance of the
+ :obj:`iris.analysis.PERCENTILE` aggregator.
+ * We've completed implementation of our :ref:`contributing.benchmarks`
+ infrastructure.
 
  And finally, get in touch with us on :issue:`GitHub<new/choose>` if you have
  any issues or feature requests for improving Iris. Enjoy!

docs/src/whatsnew/index.rst

@@ -5,13 +5,13 @@
 What's New in Iris
 ------------------
 
-.. include:: latest.rst
+.. include:: 3.3.rst
 
 .. toctree::
  :maxdepth: 1
  :hidden:
 
- latest.rst
+ 3.3.rst
  3.2.rst
  3.1.rst
  3.0.rst