Converted plugin to library

[mvanbeusekom]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Feature

⤵️ What is the current behavior?

In current version you separately have to import permission_enums.dart to get access to the PermissionGroup and PermissionStatus enums.

🆕 What is the new behavior (if this is a feature change)?

By converting the project into a library (using the library, part and part of keywords) this will no longer be necessary and the user now only needs to import the permission_handler.dart.

💥 Does this PR introduce a breaking change?

Yes (developers using the plugin need to remove the existing import 'package:permission_handler/permission_enums.dart'; line from their code to be able to compile again.

🐛 Recommendations for testing

Run the example application:

# Change into the example folder
cd example
# Run the example application
flutter run

📝 Links to relevant issues/docs

🤔 Checklist before submitting

• All projects build
• Follows style guide lines (code style guide)
• Relevant documentation was updated
• Rebased onto current develop