WCAG AA: the index's numbers row is reachable by keyboard (#181)

ddiff --git a/server/web/page.js b/server/web/page.js
iindex 7732aa7..a5768b8 100644
---- a/server/web/page.js
++++ b/server/web/page.js
@@@ -347,7 +347,7 @@ function frontShowcase(owners = DEFAULT_EVENT_OWNERS, data = null) {
  /** The front page's data sections: the numbers, the shelves of newest documents, the API and the questions. */
  function frontSections(data) {
      const stats = data ? [[data.total, 'public documents'], [data.sources, 'sites sending'], [data.kinds, 'kinds of document'], [data.week, 'added or updated this week']].filter(([n]) => n > 0) : [];
--    const statList = stats.length ? `<ul class="fs-stats" aria-label="The index in numbers">${stats.map(([n, label]) => `<li><b>${esc(fmt(n))}</b><span>${esc(label)}</span></li>`).join('')}</ul>` : '';
++    const statList = stats.length ? `<ul class="fs-stats" aria-label="The index in numbers" tabindex="0">${stats.map(([n, label]) => `<li><b>${esc(fmt(n))}</b><span>${esc(label)}</span></li>`).join('')}</ul>` : '';
      const statRow = statList ? `<section class="sc-sec fs-stats-sec">${statList}</section>` : '';
      const shelves = data && data.shelves.length ? `<section class="sc-sec" aria-labelledby="h-new"><h2 id="h-new">New on the network</h2>
  <p class="sc-lede">The newest public documents of each kind, as they reached the index.</p>