dasel: add shell completions to output

pkgs/applications/misc/dasel/default.nix

@@ -1,6 +1,7 @@
 { lib
 , buildGoModule
 , fetchFromGitHub
+, installShellFiles
 }:
 
 buildGoModule rec {
@@ -20,6 +21,15 @@ buildGoModule rec {
     "-s" "-w" "-X github.com/tomwright/dasel/v2/internal.Version=${version}"
   ];
 
+  nativeBuildInputs = [ installShellFiles ];
+
+  postInstall = ''
+    installShellCompletion --cmd dasel \
+      --bash <($out/bin/dasel completion bash) \
+      --fish <($out/bin/dasel completion fish) \
+      --zsh <($out/bin/dasel completion zsh)
+  '';
+
   doInstallCheck = true;
   installCheckPhase = ''
     runHook preInstallCheck