Add changelog

CHANGELOG/0.9.0.md

+A new version has been pushed to F-droid and TestFlight!
+
+### Changes
+- Fix the infamous `FormatException: Not a valid url: ` error!
+- Room upgrades are now handled!
+    - Upgraded rooms are now hidden from the overview
+    - To access older messages from the previous room,
+      simply scroll up: the timeline is seamless
+- Improve performance of loading the overview.
+  Opening the app should be a lot quicker now!
+- Improve performance of loading a chat
+- Add ability to swipe through images in a chat (thanks to Nathan van Beelen!)
+
+  [**See preview here!**](https://git.pattle.im/pattle/app/raw/v0.9.0/CHANGELOG/0.9.0.webm)
+
+### Get Pattle
+
+- **Android**:
+    - **F-droid**
+      1. Add the following repo in F-droid:
+
+          https://fdroid.pattle.im/?fingerprint=E91F63CA6AE04F8E7EA53E52242EAF8779559209B8A342F152F9E7265E3EA729
+
+       2. Install 'Pattle'
+    - **APK**: Download from the assets of this release
+- **iOS** (TestFlight): [Follow the instructions here!](https://testflight.apple.com/join/uTytydST)
+
+### Issues
+
+If you stumble upon any issues,
+[please report them](https://git.pattle.im/pattle/app/issues)!
+You can [login via GitHub and Gitlab.com](https://git.pattle.im/users/sign_in)
+, so it's really easy to do!
+
+### Follow development
+
+Follow development in [#app:pattle.im](https://matrix.to/#/#app:pattle.im)!
+
+### Support me
+
+If you would like to support me, you can now do so
+via [Liberapay](https://liberapay.com/wilko/) and
+[Patreon](https://www.patreon.com/pattle_app).
+
+I've invested a lot of money in making Pattle happen
+on iOS: MacBook, Apple Developer Program, and an iPhone.
+Pretty costly, so any donations will be greatly appreciated!
+
+
+### What to expect in the next release
+
+- Fix timeline jump issues
+- Remove redundant state messages when a room is upgraded
+- Start work on chat details screen (members, change name, etc.)
+- And more!
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