Android Support (#166)

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

easytier-gui/src-tauri/gen/android/build.gradle.kts

@@ -0,0 +1,22 @@
+buildscript {
+    repositories {
+        google()
+        mavenCentral()
+    }
+    dependencies {
+        classpath("com.android.tools.build:gradle:8.3.2")
+        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.21")
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+tasks.register("clean").configure {
+    delete("build")
+}
+