LibWeb: Implement Window.prompt()

Author: https://github.com/linusg
Commit: 5e07c27e25
Pull-request: https://github.com/SerenityOS/serenity/pull/5423
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/InProcessWebView.cpp

@@ -30,6 +30,7 @@
 #include <LibGUI/Action.h>
 #include <LibGUI/Application.h>
 #include <LibGUI/Clipboard.h>
+#include <LibGUI/InputBox.h>
 #include <LibGUI/MessageBox.h>
 #include <LibGUI/Painter.h>
 #include <LibGUI/ScrollBar.h>
@@ -425,4 +426,12 @@ bool InProcessWebView::page_did_request_confirm(const String& message)
     return confirm_result == GUI::Dialog::ExecResult::ExecOK;
 }
 
+String InProcessWebView::page_did_request_prompt(const String& message, const String& default_)
+{
+    String value { default_ };
+    if (GUI::InputBox::show(window(), value, message, "Prompt") == GUI::InputBox::ExecOK)
+        return value;
+    return {};
+}
+
 }