Update release notes for 9.3.0

docs/releasenotes/9.3.0.rst

@@ -1,9 +1,6 @@
 9.3.0
 -----
 
-Backwards Incompatible Changes
-==============================
-
 API Additions
 =============
 
@@ -55,11 +52,28 @@ result in a segmentation fault. This issue was introduced in Pillow 9.1.0.
 Other Changes
 =============
 
+Windows wheels
+^^^^^^^^^^^^^^
+
+This release contains wheels for Windows built using GitHub Actions.
+
+Previously they were built by `Christoph Gohlke <https://www.cgohlke.com/>`_.
+
+A huge thanks to Christoph for building Windows binaries for us for around a decade,
+plus testing, and fixing over a hundred bug fixes along the way, in addition to building
+and hosting unofficial Windows binaries for hundreds of Python projects!
+
 Added DDS ATI1, ATI2 and BC6H reading
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Support has been added to read the ATI1, ATI2 and BC6H formats of DDS images.
 
+Release GIL when converting images using matrix operations
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Python's Global Interpreter Lock is now released when converting images using matrix
+operations.
+
 Show all frames with ImageShow
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^