doc: updated changelog.

doc/changelog.dox

@@ -1067,7 +1067,8 @@ See also:
     [mosra/magnum#439](https://github.com/mosra/magnum/issues/439))
 -   Various documentation fixes (see [mosra/magnum#492](https://github.com/mosra/magnum/issues/492),
     [mosra/magnum#521](https://github.com/mosra/magnum/pull/521),
-    [mosra/magnum#563](https://github.com/mosra/magnum/pull/563))
+    [mosra/magnum#563](https://github.com/mosra/magnum/pull/563),
+    [mosra/magnum#564](https://github.com/mosra/magnum/pull/564))
 -   @ref Corrade::Utility::Debug and friends were always brought to the
     @ref Magnum namespace via a @cpp using @ce directive, but this was never
     reflected in the docs and thus hidden from users. Now it's shown in the