docs: add summary to changelog (#1037)

* docs: add summary to changelog

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* style: pre-commit fixes

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: henryiii

docs/changelog.md

@@ -4,6 +4,16 @@
 
 ### Version 1.6.0
 
+This release adds support for UHI serialization for use with the `uhi` library,
+supported in the next release of `uhi`. A new diagnostic test has been added
+in the wheel, so you can quickly check your compile of boost-histogram without
+the full test suite. Quite a few fixes are present, as well, including a fix
+for `*=`, setting a range with a scalar, setting with a callable in a slice.
+Backend changes include many new clang-tidy checks that reduce the number of
+copies and refcount changes. We now build with pybind11 3.0.
+
+This release drops support for Python 3.8, and adds Python 3.14(t), iOS, Windows ARM, and GraalPy.
+
 #### Features
 
 - Initial support for uhi's serialization [#997][], [#1030][], [#1033][], [#1034][], [#1035][]