fix: improve update manager button

lib/services/manager_api.dart

@@ -1,4 +1,5 @@
 import 'dart:io';
+import 'package:package_info_plus/package_info_plus.dart';
 import 'package:revanced_manager/constants.dart';
 import 'package:revanced_manager/services/github_api.dart';
 
@@ -6,14 +7,43 @@ class ManagerAPI {
   final GithubAPI _githubAPI = GithubAPI();
 
   Future<File?> downloadPatches() async {
-    return await _githubAPI.latestRelease(ghOrg, patchesRepo);
+    return await _githubAPI.latestReleaseFile(ghOrg, patchesRepo);
   }
 
   Future<File?> downloadIntegrations() async {
-    return await _githubAPI.latestRelease(ghOrg, integrationsRepo);
+    return await _githubAPI.latestReleaseFile(ghOrg, integrationsRepo);
   }
 
   Future<File?> downloadManager() async {
-    return await _githubAPI.latestRelease(ghOrg, managerRepo);
+    return await _githubAPI.latestReleaseFile(
+      'Aunali321',
+      'revanced-manager-flutter',
+    );
+  }
+
+  Future<String?> getLatestPatchesVersion() async {
+    return await _githubAPI.latestReleaseVersion(ghOrg, patchesRepo);
+  }
+
+  Future<String?> getLatestManagerVersion() async {
+    return await _githubAPI.latestReleaseVersion(
+      'Aunali321',
+      'revanced-manager-flutter',
+    );
+  }
+
+  Future<String> getCurrentManagerVersion() async {
+    PackageInfo packageInfo = await PackageInfo.fromPlatform();
+    return packageInfo.version;
+  }
+
+  Future<bool> hasAppUpdates(String packageName) async {
+    // TODO: get status based on last update time on the folder of this app?
+    return true;
+  }
+
+  Future<String> getAppChangelog(String packageName) async {
+    // TODO: get changelog based on last commits on the folder of this app?
+    return 'to be implemented';
   }
 }