Initial rebrand: @polkadot -> @pezkuwi (14 packages)

- Package namespace: @polkadot/* -> @pezkuwi/*
- Repository: polkadot-js/common -> pezkuwichain/pezkuwi-common
- Author: Pezkuwi Team <team@pezkuwichain.io>

Core packages:
- @pezkuwi/util (utilities)
- @pezkuwi/util-crypto (crypto primitives)
- @pezkuwi/keyring (account management)
- @pezkuwi/networks (chain metadata)
- @pezkuwi/hw-ledger (Ledger hardware wallet)
- @pezkuwi/x-* (10 polyfill packages)

Total: 14 packages
Upstream: polkadot-js/common v14.0.1

packages/util/src/is/string.ts

@@ -0,0 +1,22 @@
+// Copyright 2017-2025 @polkadot/util authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import type { AnyString } from '../types.js';
+
+/**
+ * @name isString
+ * @summary Tests for a string.
+ * @description
+ * Checks to see if the input value is a JavaScript string.
+ * @example
+ * <BR>
+ *
+ * ```javascript
+ * import { isString } from '@pezkuwi/util';
+ *
+ * console.log('isString', isString('test')); // => true
+ * ```
+ */
+export function isString (value: unknown): value is AnyString {
+  return typeof value === 'string' || value instanceof String;
+}