Add whats-new for v2023.04.0 (#7757)

Author: dcherian

doc/whats-new.rst

@@ -17,8 +17,17 @@ What's New
 
 .. _whats-new.2023.04.0:
 
-v2023.04.0 (unreleased)
------------------------
+v2023.04.0 (April 14, 2023)
+---------------------------
+
+This release includes support for pandas v2, allows refreshing of backend engines in a session, and removes deprecated backends
+for ``rasterio`` and ``cfgrib``.
+
+Thanks to our 19 contributors:
+Chinemere, Tom Coleman, Deepak Cherian, Harshitha, Illviljan, Jessica Scheick, Joe Hamman, Justus Magin, Kai Mühlbauer, Kwonil-Kim, Mary Gathoni, Michael Niklas, Pierre, Scott Henderson, Shreyal Gupta, Spencer Clark,  mccloskey, nishtha981, veenstrajelmer
+
+We welcome the following new contributors to Xarray!:
+Mary Gathoni, Harshitha, veenstrajelmer, Chinemere, nishtha981, Shreyal Gupta, Kwonil-Kim, mccloskey.
 
 New Features
 ~~~~~~~~~~~~