docs: explicitly mention extension modules defined in other specs (#72)

README.md

@@ -1,7 +1,12 @@
 # webdriver-bidi-protocol
 
 This repository contains TypeScript types conforming to the [WebDriver
-BiDi](https://w3c.github.io/webdriver-bidi/) specification.
+BiDi](https://w3c.github.io/webdriver-bidi/) specification. It also
+supports WebDriver BiDi extension modules defined in other
+specifications:
+
+- [Permissions](https://w3c.github.io/permissions/#automation-webdriver-bidi)
+- [Web Bluetooth](https://webbluetoothcg.github.io/web-bluetooth/#automated-testing)
 
 ## Installation
 
@@ -31,4 +36,4 @@ await sendCommand('browsingContext.print', {context: 'xxx'});
 ## Versioning
 
 This package patch version will be incremented whenever there are
-specification updates. 
+specification updates.