feature: import subscription from v2rayng://install-sub deeplink

V2rayNG/app/src/main/res/values-zh-rCN/strings.xml

@@ -234,5 +234,7 @@
         <item>VPN</item>
         <item>仅代理</item>
     </string-array>
+    <string name="import_subscription_success">订阅导入成功</string>
+    <string name="import_subscription_failure">导入订阅失败</string>
 
 </resources>