Add changelog

CHANGELOG.md

@@ -0,0 +1,4 @@
+# Version 0.2.3 - 2020-01-XX
+### New features
+- Added changelog
+- Added copy button

lib/views/settings.dart

@@ -155,6 +155,11 @@ class _SettingsState extends State<Settings> {
               title: Text("Help"),
               onTap: () => launch(
                   "https://gitlab.com/ChristianPauly/fluffychat-flutter/issues")),
+          ListTile(
+              leading: Icon(Icons.list),
+              title: Text("Changelog"),
+              onTap: () => launch(
+                  "https://gitlab.com/ChristianPauly/fluffychat-flutter/blob/master/CHANGELOG.md")),
           ListTile(
               leading: Icon(Icons.link),
               title: Text("License"),