translations: Add link to Japanese translation

source/mahara/translations.html

@@ -7,6 +7,7 @@
 <li><a href="https://manual.mahara.org/de/{{version}}/" title="de" alt="de">Deutsch</a></li>
 <li><a href="https://manual.mahara.org/en/{{version}}/" title="en" alt="en">English</a></li>
 <li><a href="https://manual.mahara.org/fr/{{version}}/" title="fr" alt="fr">Français</a></li>
+<li><a href="https://manual.mahara.org/ja/{{version}}/" title="ja" alt="ja">日本語</a></li>
 <li><a href="https://manual.mahara.org/nl/{{version}}/" title="nl" alt="nl">Nederlands</a></li>
 </ul>
 </div>