LibWeb: Add a helper class to work around empty execution context stack

We've peppered this workaround around the code base as needed in a few
different ways. This adds a helper class to perform this workaround in
order to simplify doing so, and ensure cleanup occurs in a RAII fashion.
This also makes it easier to grep for places where this workaround is
employed.

Userland/Libraries/LibWeb/HTML/Scripting/TemporaryExecutionContext.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/Forward.h>
+
+namespace Web::HTML {
+
+// When JS is run from outside the context of any user script, we currently do not have a running execution context.
+// This results in a crash when we access VM::running_execution_context(). This is a spec issue. Until it is resolved,
+// this is a workaround to temporarily push an execution context.
+class TemporaryExecutionContext {
+public:
+    explicit TemporaryExecutionContext(EnvironmentSettingsObject&);
+    ~TemporaryExecutionContext();
+
+private:
+    EnvironmentSettingsObject& m_environment_settings;
+};
+
+}