integration: improve Gtk>Compose subsection

- fcitx5 also allows to type accented characters with compose keys
- Accented characters can still be typed without compose keys if
  language-specific layout is used

Author: tokyo4j

src/integration.md

@@ -379,8 +379,9 @@ depending on your system setup. There are at least two ways to fallback to a
 
 ## 12.2 Compose
 
-From version `4.20.0`, accented characters cannot be typed in GTK4 applications
-without using the `ibus` package. See [#3068] for details.
+From version `4.20.0`, compose keys (e.g. typing "à" with "\`" + "a" in
+US-intl layout) do not work in GTK4 applications without using
+[input methods](#input-method) like Fcitx5 and IBus. See [#3068] for details.
 
 [#3068]: https://github.com/labwc/labwc/issues/3068