Merge branch 'development' of https://github.com/MessageKit/MessageKit into tagonsoft_development

# Conflicts:
#	Example/Sources/Data Generation/SampleData.swift

Sources/Controllers/MessagesViewController.swift

@@ -184,6 +184,8 @@ UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
         return collectionView.messagesDataSource?.numberOfItems(inSection: section, in: collectionView) ?? 0
     }
 
+    /// Note:
+    ///   If you override this method, remember to call MessagesDataSource's customCell(for:at:in:) for MessageKind.custom messages, if necessary
     open func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
 
         guard let messagesCollectionView = collectionView as? MessagesCollectionView else {
@@ -215,7 +217,7 @@ UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
             audioController.configureAudioCell(cell, message: message) // this is needed especily when the cell is reconfigure while is playing sound
             return cell
         case .custom:
-            fatalError(MessageKitError.customDataUnresolvedCell)
+            return messagesDataSource.customCell(for: message, at: indexPath, in: messagesCollectionView)
         }
     }