Add first-publish dates to demo listings.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: MaxwellBo

index.html

@@ -1861,6 +1861,7 @@ <h2>
             <p class="title">Hello, Mixbox</p>
           </a>
           <p class="description">Interactive visualisation of paint mixing</p>
+          <time>November 2022</time>
         </article>
         <article class="listing observable">
           <a href="https://observablehq.com/@mjbo/hello-spectral-js">
@@ -1869,6 +1870,7 @@ <h2>
             <p class="title">Hello, Spectral.js</p>
           </a>
           <p class="description">Another interactive visualisation of paint mixing</p>
+          <time>April 2023</time>
         </article>
         <article class="art">
           <canvas id="gameOfLife" width="256" height="256"
@@ -1882,6 +1884,7 @@ <h2>
             <p class="title">Hello, sql.js-httpvfs</p>
           </a>
           <p class="description">Utility wrapper for a SQLite.js VFS client</p>
+          <time>December 2022</time>
         </article>
         <!-- <article class="art" id="dindong">
           TEUR..ICE
@@ -1893,6 +1896,7 @@ <h2>
             <p class="title">Hello, Sparks</p>
           </a>
           <p class="description">Utility wrapper for a typeface for creating sparklines in text</p>
+          <time>November 2022</time>
         </article>
         <article class="listing observable">
           <a href="https://observablehq.com/@huw/prql">
@@ -1901,6 +1905,7 @@ <h2>
             <p class="title">Hello, PRQL</p>
           </a>
           <p class="description">Utility wrapper for an alternative SQL syntax</p>
+          <time>July 2022</time>
         </article>
         <article class="listing observable">
           <a href="https://observablehq.com/@mjbo/hello-lnjs">
@@ -1909,13 +1914,15 @@ <h2>
             <p class="title">Hello, ln.js</p>
           </a>
           <p class="description">Vector-based 3D renderer</p>
+          <time>March 2022</time>
         </article>
         <article class="listing observable">
           <a href="https://observablehq.com/@mjbo/hello-protobufjs">
             <img
               src="https://static.observableusercontent.com/thumbnail/ce388edacb37e12758548dcd21f7f7000445529bd171c36fdb64595b12a45644.jpg" />
             <p class="title">Hello, protobuf.js</p>
           </a>
+          <time>December 2022</time>
         </article>
       </div>
     </section>