LibJS: Implement evaluation of im- and exports statements

Author: https://github.com/davidot
Commit: 023968a489
Pull-request: https://github.com/SerenityOS/serenity/pull/11957
Reviewed-by: https://github.com/emanuele6
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibJS/AST.h

@@ -1344,6 +1344,8 @@ public:
     StringView name() const { return m_class_expression->name(); }
 
 private:
+    friend ExportStatement;
+
     NonnullRefPtr<ClassExpression> m_class_expression;
 };