Added fix for xcd error when launching simplefocstudio.py in reamdme

[PumaFPV]

Hey, when trying to run simplefocstudio.py I got the following error

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.

So I added the command that helped me fix it.

sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev

I'm running it on a Ubuntu VM so maybe it is why it didnt work at first. But at least it is now fixed!