Add analytics for usage of the API documentation

[teolemon]

What

Add analytics for API documentation usage

Code pointers

• https://squidfunk.github.io/mkdocs-material/setup/setting-up-site-analytics/#custom-site-analytics (MKDOCS part)
• RapidDoc ? https://openfoodfacts.github.io/openfoodfacts-server/api/ref-v2/#get-/api/v2/search
• A dedicated Matomo property has been created

<!-- Matomo -->
<script>
  var _paq = window._paq = window._paq || [];
  /* tracker methods like "setCustomDimension" should be called before "trackPageView" */
  _paq.push(['trackPageView']);
  _paq.push(['enableLinkTracking']);
  (function() {
    var u="https://analytics.openfoodfacts.org/";
    _paq.push(['setTrackerUrl', u+'matomo.php']);
    _paq.push(['setSiteId', '16']);
    var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
    g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s);
  })();
</script>
<!-- End Matomo Code -->

Part of

• Monitoring (🎯 What can I work on ? (monitoring) openfoodfacts-monitoring#1)
• 📝 API Documentation using OpenAPI (tracker) #7446