Add macOS support (#23)

* Add macOS support

* Update README

* Update to v0.2.0

* Document breaking changes

* Delete widget tests

example/macos/Flutter/Flutter-Debug.xcconfig

@@ -0,0 +1,2 @@
+#include? "Pods/Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"
+#include "ephemeral/Flutter-Generated.xcconfig"

example/macos/Flutter/Flutter-Release.xcconfig

@@ -0,0 +1,2 @@
+#include? "Pods/Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"
+#include "ephemeral/Flutter-Generated.xcconfig"

example/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -0,0 +1,16 @@
+//
+//  Generated file. Do not edit.
+//
+
+import FlutterMacOS
+import Foundation
+
+import file_picker
+import nearby_service
+import path_provider_foundation
+
+func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  FilePickerPlugin.register(with: registry.registrar(forPlugin: "FilePickerPlugin"))
+  NearbyServicePlugin.register(with: registry.registrar(forPlugin: "NearbyServicePlugin"))
+  PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
+}