[Style] Add 전처리문

Author: SHcommit

Sources/SHFirestoreService/FirestoreService.swift

@@ -5,12 +5,16 @@
 //  Created by 양승현 on 4/19/24.
 //
 
-#if os(iOS)
-import Combine
 import Foundation
 import FirebaseFirestore
 import FirebaseFirestoreCombineSwift
 
+#if os(iOS) && canImport(Combine) && swift(>=5.0)
+import Combine
+
+@available(swift 5.0)
+@available(iOS 13.0, *)
+
 public final class FirestoreService {
   // MARK: - Dependencies
   private let backgroundQueue: DispatchQueue