JS: Add support for Array.prototype.with

Note: This was authored by Copilot

javascript/ql/test/library-tests/TripleDot/array-with.js

@@ -0,0 +1,25 @@
+function t1() {
+    const arr = [1, 2, 3];
+    const newArr = arr.with(1, source('with.1'));
+    sink(newArr[1]); // $ hasValueFlow=with.1
+}
+
+function t2() {
+    const arr = [source('with.2.1'), 2, source('with.2.3')];
+    const newArr = arr.with(1, 'replaced');
+    sink(newArr[0]); // $ hasValueFlow=with.2.1
+    sink(newArr[2]); // $ hasValueFlow=with.2.3
+}
+
+function t3() {
+    const arr = [1, 2, 3];
+    const index = source('with.3.index');
+    const newArr = arr.with(index, 'new value');
+    // No assertions here as the index is tainted, not the value
+}
+
+function t4() {
+    const arr = [1, 2, 3];
+    const newArr = arr.with(1, source('with.4'));
+    sink(arr[1]); // This should NOT have value flow as with() returns a new array
+}