Package Sniffnet as AppImage

[GyulyVGC]

Package Sniffnet as AppImage, to increase the app compatibility making it more portable and distribution-agnostic for Linux users.

[GyulyVGC]

This is being implemented by @AlleM43 in #859

[DSS87]

Is that also possible as a Flatpak?

[AlleM43]

See #252 (comment) for my explanation of how that wouldn't allow for packet capture.