feat: add support for Flutter Linux, macOS and Windows (#10)

macos/Classes/Libgit2dartPlugin.swift

@@ -0,0 +1,19 @@
+import Cocoa
+import FlutterMacOS
+
+public class Libgit2dartPlugin: NSObject, FlutterPlugin {
+  public static func register(with registrar: FlutterPluginRegistrar) {
+    let channel = FlutterMethodChannel(name: "libgit2dart", binaryMessenger: registrar.messenger)
+    let instance = Libgit2dartPlugin()
+    registrar.addMethodCallDelegate(instance, channel: channel)
+  }
+
+  public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
+    switch call.method {
+    case "getPlatformVersion":
+      result("macOS " + ProcessInfo.processInfo.operatingSystemVersionString)
+    default:
+      result(FlutterMethodNotImplemented)
+    }
+  }
+}

macos/libgit2dart.podspec

@@ -0,0 +1,23 @@
+#
+# To learn more about a Podspec see http://guides.cocoapods.org/syntax/podspec.html.
+# Run `pod lib lint libgit2dart.podspec` to validate before publishing.
+#
+Pod::Spec.new do |s|
+  s.name             = 'libgit2dart'
+  s.version          = '0.0.1'
+  s.summary          = 'Dart bindings to libgit2.'
+  s.description      = <<-DESC
+Dart bindings to libgit2.
+                       DESC
+  s.homepage         = 'https://github.com/SkinnyMind/libgit2dart'
+  s.license          = { :file => '../LICENSE' }
+  s.author           = { 'Aleksey Kulikov' => 'skinny.mind@gmail.com' }
+  s.source           = { :path => '.' }
+  s.source_files     = 'Classes/**/*'
+  s.dependency 'FlutterMacOS'
+  s.vendored_libraries = '../.dart_tool/libgit2/macos/libgit2-1.3.0.dylib'
+
+  s.platform = :osx, '10.11'
+  s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES' }
+  s.swift_version = '5.0'
+end