Undo button when deleting an message with the swipe action

[N1c093]

Checklist

• I have used the search function to see if someone else has already submitted the same feature request.
• I will describe the problem with as much detail as possible.
• This issue only contains a request for one single feature, not multiple (related) features.

App version

6.502

Problem you are trying to solve

Some versions ago the newest swipe actions where build into K-9. These swipe actions are working pretty fine to mark or delete an e-mail.
Sadly when you delete an e-mail with the swipe action you can't undo it. I happens to me a few time, that I deleted a mail with the swipe action and can't undo it. I had to manually search the message in the trash folder.

Suggested solution

When you delete a message with the swipe action, there should be a small message on the buttom of the screen to undo it. This message should disappear after a few secons. Like in gmail or outlook app for android.
See example screenshot below.

Screenshots / Drawings / Technical details

[cketti]

Duplicate of #624