feat(website): mention when JSX modes were introduced

Include version numbers to reduce confusion.

website/public/errors/jsx/index.ejs.html

@@ -77,6 +77,12 @@ <h2>JSX modes</h2>
         </figcaption>
       </figure>
 
+      <p>
+        Specifying a JSX mode in quick-lint-js.config was introduced in
+        quick-lint-js version 3.1.0. Prior to version 3.1.0, the JSX mode was
+        always <code style="json">"react"</code>.
+      </p>
+
       <section id="auto">
         <h3><code style="json">"auto"</code> JSX mode</h3>
 
@@ -143,6 +149,11 @@ <h3><code style="json">"auto"</code> JSX mode</h3>
             </tr>
           </tbody>
         </table>
+
+        <p>
+          The <code style="json">"auto"</code> JSX mode was introduced in
+          quick-lint-js version 3.1.0.
+        </p>
       </section>
 
       <section id="react">
@@ -199,6 +210,12 @@ <h2>React.js (<code style="json">"react"</code> JSX mode)</h2>
           </figcaption>
         </figure>
       </section>
+
+      <p>
+        The <code style="json">"react"</code> JSX mode was introduced
+        quick-lint-js version 2.0.0. The <code style="json">"react"</code> JSX
+        mode was the default JSX mode until quick-lint-js version 3.1.0.
+      </p>
     </main>
 
     <footer><%- await include("../../common-footer-nav.ejs.html") %></footer>