add piston nix pkg for jelly

runtimes/default.nix

@@ -39,4 +39,5 @@ args: {
     "sbcl-lisp" = import ./sbcl-lisp.nix args;
     "jvm-kotlin" = import ./jvm-kotlin.nix args;
     "julia" = import ./julia.nix args;
+    "jelly" = import ./jelly.nix args;
 }

runtimes/jelly.nix

@@ -0,0 +1,26 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.jelly;
+in piston.mkRuntime {
+    language = "jelly";
+    version = pkg.version;
+    aliases = [];
+
+    run = ''
+        ${pkg}/bin/jelly fu "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.jelly" = ''
+                    “OK”
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.jelly";
+        })
+    ];
+}