Re-add Jest, revert ava (#1779)

* Re-add Jest (env node)

* Revert "Switch to ava as a test runner (#1778)"

This reverts commit 5aa2b3c096.

jest.config.cjs

@@ -0,0 +1,10 @@
+// Copyright 2020-2022 @polkadot/phishing authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+const config = require('@polkadot/dev/config/jest.cjs');
+
+module.exports = {
+  ...config,
+  moduleNameMapper: {},
+  testTimeout: 2 * 60 * 1000
+};