docs/changes: update for next release.

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 0.5.4 <https://amaranth-lang.org/docs/amaranth/v0.5.3/>`_
 * `Amaranth 0.5.3 <https://amaranth-lang.org/docs/amaranth/v0.5.3/>`_
 * `Amaranth 0.5.2 <https://amaranth-lang.org/docs/amaranth/v0.5.2/>`_
 * `Amaranth 0.5.1 <https://amaranth-lang.org/docs/amaranth/v0.5.1/>`_
@@ -22,6 +23,12 @@ Documentation for past releases of the Amaranth language and toolchain is availa
 * `Amaranth 0.3 <https://amaranth-lang.org/docs/amaranth/v0.3/>`_
 
 
+Version 0.5.4
+=============
+
+Updated to address deprecations in Yosys 0.48.
+
+
 Version 0.5.3
 =============