[fix] simple template: add ID to elements used for aria-labelledby

The ``aria-labelledby`` [1] attribute identifies the element that labels the
element it is applied to.  The templates ``infinite_scroll.html`` and
``search_on_category_select.html`` define a ``aria-labelledby`` at the <input>
tag but miss the id in the <div> with the description.

[1] https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Attributes/aria-labelledby

Signed-off-by: Markus <markus@venom.fritz.box>

searx/templates/simple/preferences/infinite_scroll.html

@@ -10,7 +10,7 @@
            {%- endif -%}{{- ' ' -}}
            >{{- '' -}}
   </p>{{- '' -}}
-  <div class="description">
+  <div class="description" id="pref_infinite_scroll">
     {{- _('Automatically load next page when scrolling to bottom of current page') -}}
   </div>{{- '' -}}
 </fieldset>{{- '' -}}

searx/templates/simple/preferences/search_on_category_select.html

@@ -10,7 +10,7 @@
            {%- endif -%}{{- ' ' -}}
            >{{- '' -}}
   </p>{{- '' -}}
-  <div class="description">
+  <div class="description" id="pref_search_on_category_select">
     {{- _('Perform search immediately if a category selected. Disable to select multiple categories') -}}
   </div>{{- '' -}}
 </fieldset>{{- '' -}}