!3 php8 兼容

Merge pull request !3 from F4nniu (FastAdmin开源框架)/php8_compatibility

library/think/Model.php

@@ -2268,27 +2268,32 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
     }
 
     // JsonSerializable
+    #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
         return $this->toArray();
     }
 
     // ArrayAccess
+    #[\ReturnTypeWillChange]
     public function offsetSet($name, $value)
     {
         $this->setAttr($name, $value);
     }
 
+    #[\ReturnTypeWillChange]
     public function offsetExists($name)
     {
         return $this->__isset($name);
     }
 
+    #[\ReturnTypeWillChange]
     public function offsetUnset($name)
     {
         $this->__unset($name);
     }
 
+    #[\ReturnTypeWillChange]
     public function offsetGet($name)
     {
         return $this->getAttr($name);