WebDriver: Implement POST /session/{id}/element/{id}/element

Author: https://github.com/TobyAsE
Commit: d26bbcab42
Pull-request: https://github.com/SerenityOS/serenity/pull/15694
Reviewed-by: https://github.com/linusg ✅

Userland/Services/WebDriver/Session.h

@@ -45,6 +45,7 @@ public:
     ErrorOr<JsonValue, HttpError> get_title();
     ErrorOr<JsonValue, HttpError> find_element(JsonValue const& payload);
     ErrorOr<JsonValue, HttpError> find_elements(JsonValue const& payload);
+    ErrorOr<JsonValue, HttpError> find_element_from_element(JsonValue const& payload, StringView parameter_element_id);
     ErrorOr<void, Variant<HttpError, Error>> close_window();
     ErrorOr<JsonValue, HttpError> get_all_cookies();
     ErrorOr<JsonValue, HttpError> get_named_cookie(String const& name);