chore: added necessary lang attributes

Author: mfranzke

index.html

@@ -213,7 +213,7 @@ <h3>
         </p>
       </section>
 
-      <section>
+      <section lang="en">
         <!-- [html-validate-disable-next heading-level -- we're doing some simple demonstration simplification here] -->
         <h2 class="elm-headline">Core principals</h2>
 
@@ -389,7 +389,7 @@ <h3 class="elm-headline">Community driven</h3>
         </ul>
       </section>
 
-      <section>
+      <section lang="en">
         <!-- [html-validate-disable-next heading-level -- we're doing some simple demonstration simplification here] -->
         <h2 class="elm-headline">How to use</h2>
         <p>