fix(searchbar): wrap search icon in button element

Align the structure of the originally served HTML more with the
resulting structure after the scripted replacement, to avoid style
shift.

Co-authored-by: Sam Arbid <36583694+Samk13@users.noreply.github.com>

Author: max-moser

invenio_app_rdm/theme/templates/semantic-ui/invenio_app_rdm/searchbar.html

@@ -55,7 +55,9 @@
                 class="prompt"
                 value=""
               >
-              <i aria-hidden="true" class="search icon"></i>
+              <button class="ui icon button right-floated search" aria-label="{{ _('Search') }}">
+                <i aria-hidden="true" class="search icon"></i>
+              </button>
             </div>
           </div>
         </div>