Add Email alias for StringEmail with usage example

- Introduced `Email` as a readonly alias for `StringEmail`.
- Updated `Usage` examples to demonstrate `Email` usage and behavior.

Author: georgedeploy

src/String/Alias/Email.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpTypedValues\String\Alias;
+
+use PhpTypedValues\String\StringEmail;
+
+/**
+ * @psalm-immutable
+ */
+readonly class Email extends StringEmail
+{
+}

src/Usage/String.php

@@ -1,5 +1,6 @@
 <?php
 
+use PhpTypedValues\String\Alias\Email;
 use PhpTypedValues\String\Alias\JsonStr;
 use PhpTypedValues\String\Alias\NonBlankStr;
 use PhpTypedValues\String\Alias\NonEmptyStr;
@@ -44,6 +45,7 @@
 echo Json::tryFromString('{}')->toString() . \PHP_EOL;
 
 // Email (usage and try* for Psalm visibility)
+echo Email::fromString('User@Example.COM')->toString() . \PHP_EOL; // normalized to lowercase
 echo StringEmail::fromString('User@Example.COM')->toString() . \PHP_EOL; // normalized to lowercase
 $em = StringEmail::tryFromString('not-an-email');
 if (!($em instanceof Undefined)) {