add php docs

Author: ginotrombetti

Diff for: src/Gateway/Model/Context.php

@@ -10,5 +10,8 @@ class Context
 {
     public string $id;
     public ?array $items;
+    /**
+     * @var Ttl $expiration
+     */
     public Ttl $expiration;
 }

Diff for: src/Registry/Model/RangeCell.php

@@ -6,5 +6,8 @@
 
 class RangeCell extends Cell
 {
+    /**
+     * @var Range $range
+     */
     public Range $range;
 }