[Bug] Documentation: Installation on Linux

### Bug Description

Hi,
First I have to admit that my setting is "strange". Lastly I use Void Linux with Hyprland WM.
I tried to get working AppFlowy with tar.gz package and AppImage, but only with Flatpak it was working properly.
By properly I mean that dialog to chose a working directory for AppFlowy was working correctly.

( skip if TLTR
I said to myself, maybe its my system problem.
I installed Xubuntu in VM and AppImage and tar.gz was working as they should.

I installed Ubuntu Server in a VM and in few steps I was testing AppFlowy.
1) Then I installed Xorg and Fluxbox - AppImage and tar.gz packages wasn't working as on my system.
2) Then I installed xfce4 - same result.
3) Then I installed xubuntu-core - and it that moment it starts to work.)

Later I figured out on my system that flatpaks dialog have zenity class.
When I installed zenity, running both AppImage and tar.gz I had no problem with directory dialog.

So: It would be nice to found in the documentation that I should install zenity.

### How to Reproduce

Use some Linux without zenity installed
and run AppFlowy from AppImage or tar.gz package.

### Expected Behavior

Without zenity - directory dialog want work;
with zenity - all is working fine.

### Operating System

Linux

### AppFlowy Version(s)

0.3.8

### Screenshots

_No response_

### Additional Context

_No response_