App: center create item modal and add dismiss button #533
Description
Currently, the create item modal isn't centered on all devices. It's probably got a fixed offset from the side right now, which we don't want. The first part of this ticket is to make it so that it's horizontally centered regardless of screen size.
The next part of this ticket is to make it so the + button that opens the modal turns into an x button while the modal is open. When the x button is pressed, the modal should get dismissed. A screenshot of the relevant parts of the Figma have been attached below, but check again just in case it's been updated since.
