fix(admin): accept multi-value 发布类型 on header-nav save

header_newposts_types is multi-select but PHP schema used type=select,
so validate() rejected arrays with 422. Use checkbox and allow
select+multiple arrays in SchemaProvider.

src/AKSRT/Admin/Schema/SchemaPageDisplay.php

@@ -58,7 +58,7 @@ class SchemaPageDisplay {
                                 ['label' => '紫色', 'value' => 'jb-purple'],
                                 ['label' => '粉色', 'value' => 'jb-pink'],
                             ]],
-                            ['key' => 'header_newposts_types', 'label' => '发布类型', 'type' => 'select', 'default' => ['post'], 'options' => [
+                            ['key' => 'header_newposts_types', 'label' => '发布类型', 'type' => 'checkbox', 'default' => ['post'], 'options' => [
                                 ['label' => '文章', 'value' => 'post'],
                                 ['label' => '帖子', 'value' => 'topic'],
                                 ['label' => '商品', 'value' => 'product'],