Update CHANGELOG to version 3.0.0

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Changelog
 
+## 3.0.0
+* Migrate to null safety
+* Minimum Dart SDK version increased to 2.12.0
+* Minimum Flutter SDK version increased to 1.20.0
+
+API changes:
+* Voximplant.getAudioDeviceManager() -> [Voximplant.audioDeviceManager](/docs/references/fluttersdk/voximplant#audioDeviceManager)
+* Voximplant.getCameraManager() -> [Voximplant.cameraManager](/docs/references/fluttersdk/voximplant/#cameraManager)
+* Voximplant.getMessenger() -> [Voximplant.messenger](/docs/references/fluttersdk/voximplant/#messenger)
+* Added named `settings` argument to [VIClient.call()](/docs/references/fluttersdk/client/viclient#call), [VIClient.conference()](/docs/references/fluttersdk/client/viclient#conference) and [VICall.answer()](/docs/references/fluttersdk/call/vicall#answer) 
+
+Other changes:
+* [VIConversation.title](/docs/references/fluttersdk/messaging/viconversation#title) field nullability changed to nullable
+* [VIConversationConfig.title](/docs/references/fluttersdk/messaging/viconversationconfig#title) field nullability changed to nullable
+* [VIAuthResult.loginTokens](/docs/references/fluttersdk/client/viauthresult#logintokens) field nullability changed to nullable
+* Minor internal improvements
+
 ## 2.6.1
 * Fix for [#20](https://github.com/voximplant/flutter_voximplant/issues/20)