Sending a message as owner from 3rd party app should mark all messages as read in matrix room

[AndrewJDR]

If you reply to a message from a native app (iMessages app, Hangouts app, etc), all messages in that matrix room should be marked as read by the puppet user.
Current behavior: Messages will remain unread until you look at them within the matrix client.

(As a side note, If the 3rd party protocol supports self-read statuses, they should be marked as read in matrix as soon as you read them using the 3rd party protocol's native app, but I'm not sure which protocols support this, if any)