[stable21.1] Changelog for 11.0 and 11.1

[backportbot-nextcloud]

11.1.0 – 2021-02-22

✅ Added

• Integrate with Deck to allow posting Deck cards to Talk conversations #5201 #5202 #5203
• Allow other apps to register message actions, e.g. Deck can create a Deck card out of a chat message #5204
• Allow to delete chat messages #5205 #5206
• Add information about callFlags of a conversation to the API so mobile clients can show if it's a audio or video call #5208

🐞 Fixed

• Prevent loading old messages twice on scroll which could skip some messages #5209