LibWeb: Implement module type allowed

This patch adds the module type allowed steps given a module type string
and an environment settings object.

Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp

@@ -1,6 +1,7 @@
 /*
  * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2022, networkException <networkexception@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -266,6 +267,19 @@ bool EnvironmentSettingsObject::is_scripting_disabled() const
     return !is_scripting_enabled();
 }
 
+// https://html.spec.whatwg.org/multipage/webappapis.html#module-type-allowed
+bool EnvironmentSettingsObject::module_type_allowed(AK::String const& module_type) const
+{
+    // 1. If moduleType is not "javascript", "css", or "json", then return false.
+    if (module_type != "javascript"sv && module_type != "css"sv && module_type != "json"sv)
+        return false;
+
+    // FIXME: 2. If moduleType is "css" and the CSSStyleSheet interface is not exposed in settings's Realm, then return false.
+
+    // 3. Return true.
+    return true;
+}
+
 // https://html.spec.whatwg.org/multipage/webappapis.html#incumbent-settings-object
 EnvironmentSettingsObject& incumbent_settings_object()
 {

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

@@ -106,6 +106,8 @@ struct EnvironmentSettingsObject
     bool is_scripting_enabled() const;
     bool is_scripting_disabled() const;
 
+    bool module_type_allowed(String const& module_type) const;
+
 protected:
     explicit EnvironmentSettingsObject(NonnullOwnPtr<JS::ExecutionContext>);