docs(package_info_plus): Add platform specific documentation (#2845)

packages/package_info_plus/package_info_plus/lib/package_info_plus.dart

@@ -92,23 +92,56 @@ class PackageInfo {
     return _fromPlatform!;
   }
 
-  /// The app name. `CFBundleDisplayName` on iOS, `application/label` on Android.
+  /// The app name.
+  ///
+  /// - `CFBundleDisplayName` on iOS and macOS, falls back to `CFBundleName`.
+  ///   Defined in the `info.plist` and/or product target in xcode.
+  /// - `application/label` on Android.
+  ///   Defined in `AndroidManifest.xml` or String resources.
+  /// - `app_name` from `version.json` on Web.
+  ///   Defined in the `manifest.json`.
+  /// - `app_name` from `version.json` on Linux.
+  ///   Defined in the `CMakeLists.txt` file.
+  /// - `ProductName` from the compiled executable file on Windows.
+  ///    Defined in the `Runner.rc` file.
   final String appName;
 
-  /// The package name. `bundleIdentifier` on iOS, `getPackageName` on Android.
+  /// The package name.
+  ///
+  /// - `bundleIdentifier` on iOS and macOS.
+  ///   Defined in the product target in xcode.
+  /// - `packageName` on Android.
+  ///   Defined in `build.gradle` as `applicationId`.
+  /// - `package_name` from `version.json` on Web and Linux
+  ///   Generated by Flutter.
+  /// - `InternalName` from the compiled executable file on Windows.
+  ///   Defined in the `Runner.rc` file.
   final String packageName;
 
-  /// The package version. `CFBundleShortVersionString` on iOS, `versionName` on Android.
+  /// The package version.
+  /// Generated from the version in `pubspec.yaml`.
+  ///
+  /// - `CFBundleShortVersionString` on iOS and macOS.
+  /// - `versionName` on Android.
+  /// - `version` from `version.json` on Web and Linux.
+  /// - `ProductVersion` from the compiled executable file on Windows.
   final String version;
 
-  /// The build number. `CFBundleVersion` on iOS, `versionCode` on Android.
+  /// The build number.
+  /// Generated from the version in `pubspec.yaml`.
+  ///
+  /// - `CFBundleVersion` on iOS and macOs.
+  /// - `versionCode` on Android.
+  /// - `build_number` from `version.json` on Web and Linux.
+  /// - `ProductVersion` from the compiled executable file on Windows.
+  ///
   /// Note, on iOS if an app has no buildNumber specified this property will return version
   /// Docs about CFBundleVersion: https://developer.apple.com/documentation/bundleresources/information_property_list/cfbundleversion
   final String buildNumber;
 
   /// The build signature.
-  /// Empty string on iOS.
   /// SHA-256 signing key signature (hex) on Android.
+  /// Empty string on all the other platforms.
   final String buildSignature;
 
   /// The installer store. Indicates through which store this application was installed.