add checkmark to the narbar of all constructed HTML

We added a checkmark all narbar's that has the make effect of
clicking on the **Nu HTML check this web page** link at the very
bottom.  This makes it much more convenient when one needs
to quickly check the HTML of a number of web pages.

Run `make www` to perform the above.

1994/index.html

@@ -125,6 +125,7 @@
   <a class="Left" href="../years.html">&uarr; top &uarr;</a>
   <a class="Left" href="../1995/index.html">1995 &rarr;</a>
   <a class="Right" href="#inventory">Inventory</a>
+  <a class="Right" href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1994%2Findex.html">&#x2713;</a>
 </div>
 
 <!-- END: this line ends content from: inc/navbar.year.mid.html -->