move prolog to nix

runtimes/prolog.nix

@@ -0,0 +1,29 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.swiProlog;
+in piston.mkRuntime {
+    language = "prolog";
+    version = pkg.version;
+
+    aliases = [
+        "plg"
+    ];
+    
+    run = ''
+        ${pkg}/bin/swipl -g true -t halt "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.pl" = ''
+                    :- write('OK'), nl.
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.pl";
+        })
+    ];
+}