UI feedback [improvements]

Thanks for the feedback, @FelixSe!

Some feedback:

• the close button for the settings modal should be on the left for macOS
• The blue 'New Item' is too prominent. I suppose most items are created in the browser anyway, a normal white button would be enough. This is like an eye magnet for an option I need like once every 2 months
• +1 for list separators. Also The hover background right next to the selected background without any margin between looks a bit odd. Maybe even remove the hover background to make it more similar to a native ListView (e.g. like in Mail)
• The items list is missing the familiar bounce back effect when you try to scroll past the beginning or end