Android Support (#166)

1. Add vpnservice tauri plugin for android.
2. add workflow for android.
3. Easytier Core support android, allow set tun fd.

tauri-plugin-vpnservice/ios/Sources/ExamplePlugin.swift

@@ -0,0 +1,20 @@
+import SwiftRs
+import Tauri
+import UIKit
+import WebKit
+
+class PingArgs: Decodable {
+  let value: String?
+}
+
+class ExamplePlugin: Plugin {
+  @objc public func ping(_ invoke: Invoke) throws {
+    let args = try invoke.parseArgs(PingArgs.self)
+    invoke.resolve(["value": args.value ?? ""])
+  }
+}
+
+@_cdecl("init_plugin_vpnservice")
+func initPlugin() -> Plugin {
+  return ExamplePlugin()
+}