Add sticker and custom emoji Q&A to readme FAQ

README.md

@@ -162,6 +162,27 @@ choco install nheko-reborn
 
 ---
 
+**Q:** How do I add stickers and custom emojis?
+
+**A:** Stickers and custom emojis are organized in image packs. There is one
+user image pack that only your account has access to and there are room image
+packs that are accessible by everyone in the room they are defined in. You can
+activate a room image pack globally to use it in any room.
+
+To manage image packs in nheko, go to the room settings and enter the Sticker &
+Emote Settings. You will see the Private pack (your user image pack) and can
+edit it there. The Shortcode is a unique identifier you use to select the image
+with and the Body is the alternate text that is displayed on clients that don't
+support images (like the alt tag in HTML images).
+
+If you have the necessary permissions you can create new room packs with the
+button at the bottom of the image pack list. They are the same as the user pack
+but you can create as many as you want and everyone in the room can use them. It
+might be a good idea to create an extra room just for your image packs to make
+sharing easier.
+
+---
+
 ### Build Requirements
 
 - Qt5 (5.15 or greater). Required for overlapping hover handlers in Qml.