Adding the default bubbled message to the bubbleBuilder

[asoap]

I've made some changes. I'm about to fork and make some changes to the bubble builder. This will allow people to add their own bubble builder which can then show the default messages. Or more importantly wrap the message with whatever widgets they want.

Just a small snippet but the bubble builder now has a defaultBubbleMessage argument.

  final Widget Function(
    Widget child, {
    required types.Message message,
    required bool nextMessageInGroup,
    required Widget defaultBubbleMessage,
  })? bubbleBuilder;

Incoming fork / pull request.

[asoap]

And pull request has been made:

#553