Autostart applications minmized

## Prerequisites
- [X] I have searched open and closed issues for duplicates.

## Feature
**Is your feature request related to a problem? Please describe.**
I start programs like Slack or Signal automatically at startup to be able to receive messages on my PC. They automatically open a windows with the latest messages, yet I am typically not interested in these as I already read them on my phone. As a result I minimize a few windows at every startup.

**Describe the solution you'd like**
I would prefer if the minimization was done automatically either by remembering the last state the windows was in during shutdown or by having the option to start application minimized. I would prefer the later option.

**Existing work**
Not sure. The question was raised at stack overflow, but hardly got any attention:
https://elementaryos.stackexchange.com/questions/15444/how-to-launch-an-app-at-startup-in-minimized-mode
There are work-a-rounds available for Ubuntu, but it looks complicated and I not applying these, as I guess it will break sooner.
https://askubuntu.com/questions/663187/how-can-i-run-a-program-on-startup-minimized