Add Leet Speak

Not too many use cases, but something I thought of (and have seen in a few skiddie malware samples).

Will also resolve #1234

tests/operations/tests/ConvertLeetSpeak.mjs

@@ -0,0 +1,33 @@
+/**
+ * @author bartblaze []
+ * @copyright Crown Copyright 2025
+ * @license Apache-2.0
+ */
+
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "Convert to Leet Speak: basic text",
+        input: "leet",
+        expectedOutput: "l337",
+        recipeConfig: [
+            {
+                op: "Convert Leet Speak",
+                args: ["To Leet Speak"]
+            }
+        ]
+    },
+    {
+        name: "Convert from Leet Speak: basic leet",
+        input: "l337",
+        expectedOutput: "leet",
+        recipeConfig: [
+            {
+                op: "Convert Leet Speak",
+                args: ["From Leet Speak"]
+            }
+        ]
+    }
+]);
+