Add changelog entry.

CHANGELOG.md

@@ -89,6 +89,7 @@ While some features like the clipboard, menus or file dialogs are not yet availa
 - Enabled Clippy checks for all targets. ([#850] by [@xStrom])
 - Added rendering tests. ([#784] by [@fishrockz])
 - Revamped CI testing to optimize coverage and speed. ([#857] by [@xStrom])
+- GTK: Refactored `Application` to use the new structure. ([#892] by [@xStrom])
 - X11: Refactored `Application` to use the new structure. ([#894] by [@xStrom])
 - X11: Refactored `Window` to support some reentrancy and invalidation. ([#894] by [@xStrom])
 
@@ -137,7 +138,8 @@ While some features like the clipboard, menus or file dialogs are not yet availa
 [#861]: https://github.com/xi-editor/druid/pull/861
 [#869]: https://github.com/xi-editor/druid/pull/869
 [#878]: https://github.com/xi-editor/druid/pull/878
-[#889]: https://github.com/xi-editor/druid/pull/899
+[#889]: https://github.com/xi-editor/druid/pull/889
+[#892]: https://github.com/xi-editor/druid/pull/892
 [#894]: https://github.com/xi-editor/druid/pull/894
 
 ## [0.5.0] - 2020-04-01