feat(loop): Add Loop corporate messenger package

Add Loop v6.0.3 - a corporate messenger distributed as a pre-built x86-64 binary.
Uses autoPatchelfHook and wrapGAppsHook3 for NixOS compatibility.

packages/loop/default.nix

@@ -0,0 +1,2 @@
+{ pkgs, ... }:
+pkgs.callPackage ./package.nix { }