Add a changelog

CHANGES.rst

+..
+	Copyright 2023 UPLEX Nils Goroll Systemoptimierung
+	SPDX-License-Identifier: BSD-2-Clause
+	See LICENSE file for full text of license
+
+===================
+About this document
+===================
+
+.. keep this section at the top!
+
+This document contains a log of noteworthy changes to libvdp_pesi from new
+to old.
+
+===================
+libvdp_pesi Changes
+===================
+
+NEXT
+----
+
+.. !13 was a regression introduced since 7.2, so it does not qualify
+   as a change herein
+
+* Achieved an "all green" coverage report (>95% by lines, 100% by
+  functions)
+
+* Added use of the new ``$Restrict`` feature from varnish-cache to
+  ensure that key pESI functions are only called from ``vcl_deliver
+  {}``.
+
+* Optimized handling of uncacheable objects: An improvement in
+  varnish-cache made it possible to avoid copying.
+
+* Fixed a bug which could surface as a panic when worker threads
+  were destroyed (`!14`_)
+
+* Improved documentation
+
+* Reduced memory required per pESI request
+
+* Various refactoring
+
+* Adjusted to vxid and other changes in varnish-cache
+
+.. _`!14`: https://gitlab.com/uplex/varnish/libvdp-pesi/-/issues/14
+
+1097f6f48a8ea89fed89227965d94f630fb93c1f / 7.2 branch
+-----------------------------------------------------
+
+Base of the changelog