📝 added Arch Linux and Nix installation instructions to README

[LaurenzBeck]

💬 Description

Added Arch Linux and Nix installation instructions to README

❗ Issue Links

Fixes #90

🧪 How Has This Been Tested?

I was not able to test this, since I only have a windows machine. I got the installation commands from the corresponding websites.

✅ Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have made corresponding changes to the documentation

[firefly-cpp]

Thanks. The correct command for Arch/AUR ecosystem is yay -Syyu python-niaaml