Fix shortcuts and add Discord integration

First: Sorry, shortcuts on Linux were not working.

To develop the shortcuts I installed libraries ("apt install") which add libraries to my operating system, but they are, obviously, not included while exporting this project... My bad.

My lack of skills with C++, SCons and Libraries contribute to missing this important detail.

Second: I added an integration with Discord Social SDK, but I do not recommend it.

My wish was to make the application listen to your current voice chat on Discord, but this SDK doesn't do that. It exists to make games use the Discord voice/text chat infrastructure (respecting others privacy).

Third: This project is done.

I may fix bugs, add translations, add little details... But this project already took too much of my time 🤣.

It was really interesting to:

• Create a Godot wrapper around Discord Social SDK
• Create a Godot addon to listen to key strikes in X11 & Windows

But I'm tired...