chore: bump PHP requirement to 8.1+, use first-class callables

Raise minimum PHP version from 8.0 to 8.1 in composer.json and
use first-class callable syntax (self::method(...)) for array_map
calls in the Email constructor.

Author: ChiragAgg5k

composer.json

@@ -22,7 +22,7 @@
     }
   },
   "require": {
-    "php": ">=8.0.0",
+    "php": ">=8.1.0",
     "ext-curl": "*",
     "ext-openssl": "*",
     "phpmailer/phpmailer": "6.9.1",

composer.lock

@@ -48,9 +48,9 @@ public function __construct(
         private ?array $attachments = null,
         private bool $html = false,
     ) {
-        $this->to = \array_map([self::class, 'normalizeRecipient'], $to);
-        $this->cc = !\is_null($cc) ? \array_map([self::class, 'normalizeRecipient'], $cc) : null;
-        $this->bcc = !\is_null($bcc) ? \array_map([self::class, 'normalizeRecipient'], $bcc) : null;
+        $this->to = \array_map(self::normalizeRecipient(...), $to);
+        $this->cc = !\is_null($cc) ? \array_map(self::normalizeRecipient(...), $cc) : null;
+        $this->bcc = !\is_null($bcc) ? \array_map(self::normalizeRecipient(...), $bcc) : null;
 
         if (\is_null($this->replyToName)) {
             $this->replyToName = $this->fromName;