add: apple container build target

overlays/container.nix

@@ -0,0 +1,10 @@
+final: prev: {
+  containerLatest = prev.container.overrideAttrs (oldAttrs: rec {
+    version = "1.3.1";
+
+    src = prev.fetchurl {
+      url = "https://github.com/apple/container/releases/download/${version}/container-${version}-installer-signed.pkg";
+      hash = "sha256-p8G515J9MIdfL2x70dDLBsLapspXzp6QpRROiY/fVKg=";
+    };
+  });
+}