Added widget with just a sync icon

[ArnyminerZ]

Purpose

Some people is requesting a simple square widget to run synchronization for DAVx⁵ manually, this adds a new widget to extend the existing one.

Short description

Added a new widget with just an icon, that runs synchronization when clicked:

Screenshot

This doesn't exclude the already existing one with a label, but gives a new simpler option to the users.

TODO:

• For some reason both widgets have the same label, it would be cool to be able to differentiate them.

  Fixed

  

• It would be cool to show a proper preview to know how the widget will look like.

  Fixed

  

Checklist

• The PR has a proper title, description and label.
• I have self-reviewed the PR.
• I have added documentation to complex functions and functions that can be used by other modules.
• I have added reasonable tests or consciously decided to not add tests.

[ArnyminerZ]

Not really a thing that needs to be done quickly, but at least it's something, and since those files are pretty much never modified, we can just leave this ready until we want to merge it.

[sunkup]

Looks nice, but wow that is a lot of new code. I can't help but think it would be less if we had only one widget.

Is it hard to make it one widget only, which resizes and then simply hides and shows the text depending on the widget size? Without the text they are exactly the same, no?

Also, does it need to be a circle? When adding the widget I can see the widget as a square, with/without rounded borders (depending on the widget settings) for a very short time before it goes back to circle again. I could think of users who want it to behave like the other widgets do. That is to have a full background color for the widget which is cropped by the widget setting and not enforce the rounded corners (circle shape) ourselves.

I took the screenshot at the right moment, but it turns back into a circle right after:

Show screenshot

[ArnyminerZ]

Is it hard to make it one widget only, which resizes and then simply hides and shows the text depending on the widget size?

No, it should be easy, but I think @devvv4ever told me to have two different widgets, in case anyone wants a small widget with text

[ArnyminerZ]

Also, does it need to be a circle?

Not technically, but I guess we can choose