Added 'XKCD Random Number' operation

src/core/operations/XKCD.js

@@ -0,0 +1,26 @@
+/**
+ * XKCD operations.
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ *
+ * @namespace
+ */
+const XKCD = {
+
+    /**
+     * XKCD Random Number operation.
+     *
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {number}
+     */
+    runRandomNumber: function(input, args) {
+        return 4; // chosen by fair dice roll.
+                  // guaranteed to be random.
+    },
+
+};
+
+export default XKCD;