Add liquid-swap tool

pkgs/liquid-swap/default.nix

@@ -0,0 +1,17 @@
+{ lib, buildPythonPackage, fetchurl, pyqt5, click }:
+
+buildPythonPackage rec {
+  pname = "liquid-swap";
+  version = "0.0.1";
+
+  # We're only interested in the cli and not the gui but we need to add pyqt5
+  # anyway as a build dependency because liquid-swap's setup.py demands it. See
+  # issue https://github.com/Blockstream/liquid-swap/issues/1.
+  nativeBuildInputs = [ pyqt5 ];
+  propagatedBuildInputs = [ click ];
+
+  src = fetchurl {
+    urls = [ "https://github.com/Blockstream/liquid-swap/archive/release_${version}.tar.gz" ];
+    sha256 = "c90ba78105469273fb799f412caa754d18bfa310984fa11ffd0091f146cca2ba";
+  };
+}