Migrate to Declarative Plugins Block in Gradle, Replacing Deprecated apply Method

[may-tas]

Resolves #66 :

• Replaced the deprecated apply script method for app_plugin_loader in the android/build.gradle file with the declarative plugins block as recommended by Flutter's Gradle plugin migration guide.
• Ensures future compatibility with upcoming Gradle releases by adopting the new syntax for applying plugins.

P.S : ( Unrelated to the PR )

• If anybody is having trouble while running the app due to an error "google_api_headers:compileDebugKotlin failed" ,
  just go to the mentioned package "google_api_headers" directory and in the android folder , open build.gradle and paste the same compileOptions and kotlinOptions as given in app's build.gradle.
• This will fix the issue and your app will run fine.

[github-actions]

🎉🎉 Thank you for your contribution! Your PR #69 has been merged! 🎉🎉