To post issue's edit information in slack threads only

[andreevgrisha]

Add options (or default) to post slack message about any issue's edit info in thread mode only.
It's mess in a channel when info about new issue and issue's changes in one level.
Thank you!

[webxid]

The same thing.

We have tryed to implement ticket system, based on the plugin. We need to notify about a ticket creation only. But the plugin spams into a chat about each issue update.

It is ok to get notification into issue thread.
But, It whould be usefull to have a setting to switch on/off the notifications about issue updates as a separate messages into a channel.