docs: update changelog.

Author: whitequark

docs/changes.rst

@@ -9,6 +9,7 @@ Documentation for past releases
 
 Documentation for past releases of the Amaranth language and toolchain is available online:
 
+* `Amaranth 0.5.7 <https://amaranth-lang.org/docs/amaranth/v0.5.7/>`_
 * `Amaranth 0.5.6 <https://amaranth-lang.org/docs/amaranth/v0.5.6/>`_
 * `Amaranth 0.5.5 <https://amaranth-lang.org/docs/amaranth/v0.5.5/>`_
 * `Amaranth 0.5.4 <https://amaranth-lang.org/docs/amaranth/v0.5.4/>`_
@@ -25,6 +26,12 @@ Documentation for past releases of the Amaranth language and toolchain is availa
 * `Amaranth 0.3 <https://amaranth-lang.org/docs/amaranth/v0.3/>`_
 
 
+Version 0.5.8
+=============
+
+Updated to address compatibility with Python 3.14.
+
+
 Version 0.5.7
 =============