[Ring] Edit last message

[Óvári]

Hello,

This relates to the file transfer feature in Ring advertised at:
https://ring.cx/en/news#messaging-improvement-on-android

Please enable pressing the up arrow (on ring-gnome) to edit the last 
sent message. There are user who would really appreciated this feature. 
For other user who do not like this feature, they would not need to use 
this feature. It would help "with the goal of making using Ring as 
pleasant as possible for every user."

Thank you