Welcome screen at first start

[AlexPerathoner]

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Is your feature request related to a problem? Please describe

.

Describe the solution you'd like

On first start a window (not the settings window) should appear with following info:

1. thanks for download etc
2. links to repo and contributors
3. checkbox to hide the menu bar, and instructions on how to open the settings if enabled

Also add same checkbox in settings > general

Describe alternatives you've considered

No response

Anything else?

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