Documentation updates for v3.4.0rc0 release. (#5078)

* Finalise v3.4 What's New.

* Update What's New index.

* 3.4 what's new small search engine change.

* Hard-coded release information in What's New.

Author: trexfeathers

docs/src/whatsnew/latest.rst renamed to docs/src/whatsnew/3.4.rst

@@ -1,7 +1,7 @@
 .. include:: ../common_links.inc
 
-|iris_version| |build_date| [unreleased]
-****************************************
+v3.4 (17 Nov 2022) [release candidate]
+**************************************
 
 This document explains the changes made to Iris for this release
 (:doc:`View all changes <index>`.)
@@ -14,9 +14,22 @@ This document explains the changes made to Iris for this release
    :animate: fade-in
    :open:
 
-   The highlights for this major/minor release of Iris include:
-
-   * N/A
+   The highlights for this minor release of Iris include:
+
+   * We have **archived older Iris documentation** - everything before
+     ``v3.0.0`` - so older versions will soon no longer appear in search
+     engines. If you need this older documentation: please
+     see :ref:`iris_support`.
+   * We have added a :ref:`glossary` to the Iris documentation.
+   * We have completed work to make **Pandas interoperability** handle
+     n-dimensional :class:`~iris.cube.Cube`\s.
+   * We have **begun refactoring Iris' regridding**, which has already improved
+     performance and functionality, with more potential in future!
+   * We have made several other significant `🚀 Performance Enhancements`_.
+   * Please note that **Iris cannot currently work with the latest NetCDF4
+     releases**. The pin is set to ``<v1.6.1``, due to incompatibility with
+     Iris' lack of thread safety. We're working hard to make Iris NetCDF
+     loading thread safe as soon as possible.
 
    And finally, get in touch with us on :issue:`GitHub<new/choose>` if you have
    any issues or feature requests for improving Iris. Enjoy!
@@ -226,8 +239,9 @@ This document explains the changes made to Iris for this release
 #. `@tkknight`_ updated the links for the Iris documentation to v2.4 and
    earlier to point to the archive of zip files instead. (:pull:`5064`)
 
-#. `@Esadek-MO`_ added notes at the bottom of functions to
-   to clarify if the function preserves laziness or not. (:pull:`5066`)
+#. `@Esadek-MO`_ began adding notes at the bottom of functions to
+   to clarify if the function preserves laziness or not. See :issue:`3292` for
+   the ongoing checklist. (:pull:`5066`)
 
 💼 Internal
 ===========

docs/src/whatsnew/index.rst

@@ -5,13 +5,13 @@
 What's New in Iris
 ------------------
 
-.. include:: latest.rst
+.. include:: 3.4.rst
 
 .. toctree::
    :maxdepth: 1
    :hidden:
 
-   latest.rst
+   3.4.rst
    3.3.rst
    3.2.rst
    3.1.rst