Added AppImage for amd64

Created by: Schmiddiii

I think I have made a working AppImage for arm64. I cannot include the file in this text, so you have to compile it yourself to try it.

Compilation steps (docker, rust, cross, appimage-builder have to be installed)

• docker build -t tubefeeder/amd64 docker -f docker/Dockerfile_amd64
• cross build --target=x86_64-unknown-linux-gnu --release
• cd AppImage
• appimage-builder --recipe AppImageBuilder_amd64.yml
• ./Tubefeeder-latest-x86_64.AppImage

Please let me know when you cannot compile it yourself, we will find a way to share the compiled AppImage.

Closes #13 (closed)