refactor: Lint Swift (#1613)

# Description

Closes #1587

.github/workflows/test.yml

@@ -108,6 +108,13 @@ jobs:
           DEFAULT_BRANCH: main
           VALIDATE_KOTLIN_ANDROID: true
           VALIDATE_CLANG_FORMAT: true
+      - name: Lint Swift
+        # TODO: check if swift-format can be integrated in super-linter, as soon as Alpine is supported
+        # https://github.com/apple/swift-docker/issues/231
+        # https://github.com/super-linter/super-linter/pull/4568
+        run: |
+          docker run --rm --workdir=/work --volume=$PWD:/work mtgto/swift-format:5.8 \
+           lint --parallel --strict --recursive packages/audioplayers_darwin
 
   web:
     runs-on: ubuntu-latest

.swift-format

@@ -0,0 +1,4 @@
+{
+    "_comment": "details can be found at: https://github.com/apple/swift-format/blob/main/Documentation/Configuration.md",
+    "version": 1
+}

contributing.md

@@ -136,7 +136,11 @@ Once your feature got approved to start developing, feel free to send your PRs!
 
  * Start your PR title with a [conventional commit](https://www.conventionalcommits.org) type (feat:, fix: etc).
  * Your build must pass. Please make sure everything is green!
- * Follow guidelines. For the Dart side, follow [Flame's official style guide](https://github.com/flame-engine/flame/blob/main/doc/development/style_guide.md). We don't have a code analyzer for the native side (yet!), but please follow the code around you to make it properly formatted and linted. There is nothing worse than badly formatted code!
+ * Follow guidelines. For the Dart side, follow [Flame's official style guide](https://github.com/flame-engine/flame/blob/main/doc/development/style_guide.md). 
+   We also provide code linting and formatting for the native side, where we take the [Flutter's formatting](https://github.com/flutter/packages/blob/main/script/tool/lib/src/format_command.dart) as reference:
+   * C/C++: [Chromium coding style](https://chromium.googlesource.com/chromium/src/+/refs/heads/main/styleguide/c++/c++.md) via [clang-format](https://clang.llvm.org/docs/ClangFormatStyleOptions.html), available for [CLion](https://www.jetbrains.com/help/clion/clangformat-as-alternative-formatter.html) and [VSCode](https://code.visualstudio.com/docs/cpp/cpp-ide#_code-formatting)
+   * Kotlin: [Kotlin style guide](https://developer.android.com/kotlin/style-guide) via [ktlint](https://github.com/pinterest/ktlint) and [EditorConfig](https://editorconfig.org/), available for [IntelliJ](https://www.jetbrains.com/help/idea/editorconfig.html) and [VSCode](https://marketplace.visualstudio.com/items?itemName=EditorConfig.EditorConfig)
+   * Swift: [Google Swift Style Guide](https://google.github.io/swift/) via [swift-format](https://github.com/apple/swift-format), available for [VSCode](https://marketplace.visualstudio.com/items?itemName=vknabel.vscode-apple-swift-format) or CLI with [native installation](https://github.com/apple/swift-format#getting-swift-format) or [Docker](https://github.com/mtgto/docker-swift-format/tree/main)
  * Write clean, beautiful and easy to understand code, with comments if necessary and docs if applicable.
  * Update our README/getting started/feature parity table/any other docs accordingly to your change, making it clear which platforms are supported.
  * Try to support all platforms where it makes sense. This is a hard thing to ask, and we understand and we will merge PRs that only work on one platform as well. But if you have the time, please help us with feature parity.

packages/audioplayers/example/ios/Podfile.lock

@@ -41,10 +41,10 @@ PODS:
   - path_provider_foundation (0.0.1):
     - Flutter
     - FlutterMacOS
-  - SDWebImage (5.13.4):
-    - SDWebImage/Core (= 5.13.4)
-  - SDWebImage/Core (5.13.4)
-  - SwiftyGif (5.4.3)
+  - SDWebImage (5.17.0):
+    - SDWebImage/Core (= 5.17.0)
+  - SDWebImage/Core (5.17.0)
+  - SwiftyGif (5.4.4)
 
 DEPENDENCIES:
   - audioplayers_darwin (from `.symlinks/plugins/audioplayers_darwin/ios`)
@@ -79,9 +79,9 @@ SPEC CHECKSUMS:
   file_picker: ce3938a0df3cc1ef404671531facef740d03f920
   Flutter: f04841e97a9d0b0a8025694d0796dd46242b2854
   integration_test: 13825b8a9334a850581300559b8839134b124670
-  path_provider_foundation: c68054786f1b4f3343858c1e1d0caaded73f0be9
-  SDWebImage: e5cc87bf736e60f49592f307bdf9e157189298a3
-  SwiftyGif: 6c3eafd0ce693cad58bb63d2b2fb9bacb8552780
+  path_provider_foundation: 29f094ae23ebbca9d3d0cec13889cd9060c0e943
+  SDWebImage: 750adf017a315a280c60fde706ab1e552a3ae4e9
+  SwiftyGif: 93a1cc87bf3a51916001cf8f3d63835fb64c819f
 
 PODFILE CHECKSUM: ef19549a9bc3046e7bb7d2fab4d021637c0c58a3
 

packages/audioplayers/example/ios/Runner/AppDelegate.swift

@@ -1,5 +1,5 @@
-import UIKit
 import Flutter
+import UIKit
 
 @UIApplicationMain
 @objc class AppDelegate: FlutterAppDelegate {

packages/audioplayers/example/macos/Podfile.lock

@@ -22,7 +22,7 @@ EXTERNAL SOURCES:
 SPEC CHECKSUMS:
   audioplayers_darwin: dcad41de4fbd0099cb3749f7ab3b0cb8f70b810c
   FlutterMacOS: 8f6f14fa908a6fb3fba0cd85dbd81ec4b251fb24
-  path_provider_foundation: c68054786f1b4f3343858c1e1d0caaded73f0be9
+  path_provider_foundation: 29f094ae23ebbca9d3d0cec13889cd9060c0e943
 
 PODFILE CHECKSUM: 353c8bcc5d5b0994e508d035b5431cfe18c1dea7