Add package to Ubuntu installation guide

[PanderMusubi]

Describe the bug
Following the steps results in not starting the UI because of a missing package.

To Reproduce
Steps to reproduce the behavior:

1. Follow the steps for Ubuntu
2. Run the UI

Expected behavior
UI should start but reports

$ streamdeck
qt.qpa.plugin: From 6.5.0, xcb-cursor0 or libxcb-cursor0 is needed to load the Qt xcb platform plugin.
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, offscreen, wayland-egl, minimal, linuxfb, minimalegl, xcb, vkkhrdisplay, wayland, vnc.

Aborted (core dumped)

If fixed when libxcb-cursor0 is installed. That sould be added to the manual.

Screenshots
n/a

Operating system (please complete the following information)
Ubuntu 22.04
streamdeck 0.9.4
streamdeck-ui 2.0.15

Stream Deck Version
n/a