Add new tray icons for macOS

[rak-phillip]

This adds new template icons for use in the tray for macOS.

I received an icon set that represents different states (one for starting, started, stopping, stopped, and error), and I noticed that we don't necessarily have corresponding icons in windows. We don't really make use of stopped and stopping anywhere in the project, but I was thinking that it might be a good idea to get the remaining icons now for ease of use.

Alternatively, we can remove stopped and stopping from the macOS collection.

#236

[rak-phillip]

Here's some examples of the new icons. I tried to include a blue-ish background to make a fair comparison

[jandubois]

We don't really make use of stopped and stopping anywhere in the project

I think the problem is that "stopping" is taking a very short amount of time, and then the app exits, so there is no way to show the "stopped" state.

I was going to create an issue about our mental app model (do we have one or two apps (gui and background/helper/...), and what is the relationship between them from the user's point of view (like what does it mean to stop one vs. the other). But I haven't been able to clarify my own thinking about it enough to actually write it up.

[mook-as]

Please add the DCO trailer. The run logs has instructions.

[mook-as]

I assume this should be readonly as well?

[rak-phillip]

I agree - updated to include the readonly modifier

[mattfarina]

I like the stopping and stopped ones. I don't know if we'll have a case where we can show stopped. We can investigate that in the future.

These look better than what we have today.