feat: use local firebase_core instead of remote SPM dependency

Author: SelaseKay

Package.swift

@@ -9,7 +9,6 @@ import PackageDescription
 
 let library_version = "6.1.3"
 let firebase_sdk_version: Version = "12.9.0"
-let shared_spm_version: Version = "4.5.0-firebase-core-swift"
 
 let package = Package(
   name: "cloud_firestore",
@@ -21,15 +20,14 @@ let package = Package(
   ],
   dependencies: [
     .package(url: "https://github.com/firebase/firebase-ios-sdk", from: firebase_sdk_version),
-    .package(url: "https://github.com/firebase/flutterfire", exact: shared_spm_version),
+    .package(name: "firebase_core", path: "../firebase_core"),
   ],
   targets: [
     .target(
       name: "cloud_firestore",
       dependencies: [
         .product(name: "FirebaseFirestore", package: "firebase-ios-sdk"),
-        // Wrapper dependency
-        .product(name: "firebase-core-shared", package: "flutterfire"),
+        .product(name: "firebase-core", package: "firebase_core"),
       ],
       resources: [
         .process("Resources"),