added missing normative/informative class in intro

Author: pchampin

index.html

@@ -320,7 +320,7 @@ <h2>Typographical conventions</h2>
     <div data-include="common/typographical-conventions.html"></div>
   </section>
 
-  <section>
+  <section class="normative">
     <h2>Terminology</h2>
 
     <p>This document uses the following terms as defined in JSON [[RFC8288]]. Refer
@@ -342,7 +342,7 @@ <h4>Algorithm Terms</h4>
 
   </section>
 
-  <section>
+  <section class="informative">
     <h3>Example Conventions</h3>
     <p>Note that in the examples used in this document, output
       is of necessity shown in serialized form as JSON. While the algorithms