os: add test for signals constant immutability

Author: Xstoudi

test/parallel/test-os-constants-signals.js

@@ -0,0 +1,12 @@
+'use strict';
+
+const common = require('../common');
+const { test } = require('node:test');
+const assert = require('node:assert');
+const { constants } = require('node:os');
+
+const { internalBinding } = require('internal/test/binding');
+
+test('Verify that signals constant is immutable', () => {
+    assert.throws(() => constants.signals.FOOBAR = 1337, TypeError);
+})