Added possiblity to override channel list delegate methods

Author: martinmitrevski

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelViewModel.swift

@@ -146,7 +146,7 @@ open class ChatChannelViewModel: ObservableObject, MessagesDataSource {
         scrolledId = messages.first?.messageId
     }
 
-    public func handleMessageAppear(index: Int) {
+    open func handleMessageAppear(index: Int) {
         if index >= messages.count {
             return
         }

Sources/StreamChatSwiftUI/ChatChannelList/ChatChannelListViewModel.swift

@@ -216,14 +216,14 @@ open class ChatChannelListViewModel: ObservableObject, ChatChannelListController
         handleChannelListChanges(controller)
     }
 
-    public func controller(
+    open func controller(
         _ controller: ChatChannelListController,
         shouldAddNewChannelToList channel: ChatChannel
     ) -> Bool {
         channel.membership != nil
     }
 
-    public func controller(
+    open func controller(
         _ controller: ChatChannelListController,
         shouldListUpdatedChannel channel: ChatChannel
     ) -> Bool {