Recenter dock items when dock width is set to a fixed value

[purpasmart96]

When you use the width attribute for the Dock/systray like this

<Dock width=24/>

You do indeed get the proper size for the dock items. However, now they are no longer properly aligned to the middle of the tray and are instead being pushed to the top

My attempt to resolve this issue is by adding an x or y offset to the dock window when it gets resized.

Here is the fix: purpasmart96@c2f301e

My fix seems to work, but I would like to hear some feedback before submitting a PR, as per your guidelines.

[joewing]

Thanks for fixing this! That fix looks good to me. Please feel free to open a PR and I'll merge it in.

[purpasmart96]

Great! I will go ahead and do that!