Include error changes in the changelog

Author: rhpvorderman

CHANGELOG.rst

@@ -27,6 +27,10 @@ that PyPy is no longer supported.
   faster.
 + igzip.decompress has 30% less overhead when called.
 + ISA-L library version variables are now available on windows as well.
++ ``isal_zlib`` functions now raise ``isal_zlib.error`` on error. 
+  ``isal_zlib.IsalError`` has been removed.
++ The base class for ``isal_zlib.error`` and ``igzip_lib.IsalError`` is now 
+  ``Exception`` instead of ``OSError``.
 + Wheels are now always build with nasm for the x86 architecture. Previously
   yasm was used for Linux and MacOS due to build issues that have since been
   fixed upstream.