Add support for Swift package manager

[EchoEllet]

Swift Package Manager support

Support for SPM has already been added to most Flutter plugins and was included in the stable release a while ago. Soon, support for CocoaPods will be deprecated and removed at some point. This PR doesn't remove support for CocoaPods and maintains backward compatibility.

The package macos_ui still depends on appkit_ui_element_colors, which doesn't support the Swift Package Manager yet, but the PR Adrian-Samoticha/appkit_ui_element_colors#2 should fix the issue.

The changes made in this PR follow the Flutter guide for plugin authors.

The example app has been tested with both CocoaPods and SPM. I also ran the following commands:

pod lib lint macos/macos_window_utils.podspec  --configuration=Debug --skip-tests --use-modular-headers --use-libraries
pod lib lint macos/macos_window_utils.podspec  --configuration=Debug --skip-tests --use-modular-headers

Related Issues

• Fix Swift Package Manager support #52
• Related Swift Package Manager support Adrian-Samoticha/appkit_ui_element_colors#1

Other changes

This PR makes some other minor related changes:

• Excluding Swift package manager files from version control.
• Adding an empty privacy manifest file, most Flutter plugins have this, including url_launcher. This will become required even for macOS (see [various] Adds macOS privacy manifests flutter/packages#7687).
• Adding Swift package manager integration for the example app, updating some files, and upgrading the Xcode project to run the macOS app.
• Importing AppKit where needed, this is required by the Swift package manager to access macOS APIs such as NSWindow.
• Example changes are fully automated when running flutter run -d macos.

[Adrian-Samoticha]

This is immensely helpful as I haven’t yet had the time to familiarize myself with the Swift package manager. Thanks a lot; I will review both PRs soon. :)

[EchoEllet]

familiarize myself with the Swift package manager

Reading Swift Package Manager for plugin authors by Flutter is usually enough. If you have questions regarding any change and why it was introduced, please let me know.

[Adrian-Samoticha]

Alright, I merged it. However, the same issue that’s present in macos_ui (that podfile being mentioned in the readme) is present here as well. I’ll open an issue about it.