feat(admin): 新增搜索表单多选功能 add xmSelect plugin support for multiple selection

- Add xmSelect case handling in AdminController for 'in' operation
- Include xmSelect.js in admin layout
- Update easy-admin.js to support xmSelect initialization and data binding
- Modify goods.js to demonstrate xmSelect usage with simulated data
- Adjust public.css for better styling of xmSelect elements

Signed-off-by: wolfcode <37436228+wolf-leo@users.noreply.github.com>

app/common/controller/AdminController.php

@@ -190,6 +190,9 @@ class AdminController extends BaseController
                 case '%*':
                     $where[] = [$key, 'LIKE', "%{$val}"];
                     break;
+                case 'in':
+                    $where[] = [$key, 'IN', $val];
+                    break;
                 case 'range':
                     [$beginTime, $endTime] = explode(' - ', $val);
                     $where[] = [$key, '>=', strtotime($beginTime)];