Add Metrics footer (#452)

* add website to authors

* add doi back

* Update CITATION.cff

* Update footer-menu.html

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

_templates/footer-menu.html

@@ -26,6 +26,9 @@ <h1>{{ _("About") }}</h1>
               >{{ _("How to Cite") }}</a
             >
           </li>
+          <li>
+            <a href="https://projectpythia.org/metrics">{{ _("Metrics") }}</a>
+          </li>
         </ul>
       </div>
       <div class="col-9 col-sm-4 col-md-4 col-lg-3 footer-menu-col">