Add compression option to Auto upload

### Feature request
I'm always a bit frustrated while using auto upload to upload my photos on a slow WiFi-connection. On holidays for example. It can take ages. On holidays I just want to save my photos daily. It's okay for me to have them saved at 80 or 90 % so they upload faster because of the smaller file size. Once home, I'll transfer the full size photos via USB to my computer.

### A possible solution
Add a compression percentage in the modal "Preferences for auto uploading" (Menu --> Auto upload --> 3 dots at the right of a certain folder --> Configure). Like 80 or 90%, so that photos are much smaller in file size before they will be uploaded.

_Note: I'm not sure about the speed of this compression action. Especially on low end devices. And I'm not sure if you need to save the compressed image temporarily and what consequences that would bring._

### Alternatives I've considered
I've tried to find an app that listens to my photos folder and compresses new photos to a different folder called "Compressed Photos". Then I would enable auto upload in the Nextcloud app for "Compressed Photos" and disable auto upload for my normal photos folder.