feat(docs): add faq about non-UI thread use case (#130)

* feat(docs): add faq about non-UI thread use case

* Update README.md

---------

Co-authored-by: e271828- <[email protected]>

README.md

@@ -4,7 +4,7 @@
 [![Release](https://jitpack.io/v/hcaptcha/hcaptcha-android-sdk.svg)](https://jitpack.io/#hcaptcha/hcaptcha-android-sdk)
 [![Minimal Android OS](https://img.shields.io/badge/Android%20OS%20-%3E=4.1-blue.svg)](https://developer.android.com/about/dashboards)
 
-###### [Installation](#installation) | [Requirements](#requirements) | [Example App](#example-app) | [Usage](#usage) | [Customization](#config-params) | [Error Handling](#error-handling) | [Debugging](#debugging-tips) | [Testing](#testing) | [Publishing](#publishing)
+###### [Installation](#installation) | [Requirements](#requirements) | [Example App](#example-app) | [Usage](#usage) | [Customization](#config-params) | [Error Handling](#error-handling) | [Debugging](#debugging-tips) | [Testing](#testing) | [Publishing](#publishing) | [FAQ](#faq)
 
 This SDK provides a wrapper for [hCaptcha](https://www.hcaptcha.com). It is a drop-in replacement for the SafetyNet reCAPTCHA API. You will need to configure a `site key` and a `secret key` from your hCaptcha account in order to use it.
 
@@ -307,6 +307,14 @@ After retrieving a `token`, you should pass it to your backend in order to verif
 
 ---
 
+## FAQ
+
+> Can I get a token in a non-UI thread?
+
+No: the SDK depends on WebView, which is a UI component and cannot be instantiated in a non-UI thread.
+
+However, the SDK provides a completely silent (invisible to the end-user) mechanism with `hideDialog=true` config + "passive" site key (this is an Enterprise feature). But note that the token request still has to be called from the UI thread.
+
 ## For maintainers
 
 If you plan to contribute to the repo, please see [MAINTAINERS.md](./MAINTAINERS.md) for detailed build, test, and release instructions.