Add explanation for Popularity field in search results

Fixes FS#45327.
Signed-off-by: Leonidas Spyropoulos <artafinde@gmail.com>
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

web/html/css/aurweb.css

@@ -85,3 +85,8 @@ legend {
 p.important {
 	font-weight: bold;
 }
+
+span.hover-help {
+	border-bottom: 1px dotted black;
+	cursor:help;
+}

web/template/pkg_search_results.php

@@ -35,7 +35,7 @@ if (!$result): ?>
 					<th><a href="?<?= mkurl('SB=n&SO=' . $SO_next) ?>"><?= __("Name") ?></a></th>
 					<th><?= __("Version") ?></th>
 					<th><a href="?<?= mkurl('SB=v&SO=' . $SO_next) ?>"><?= __("Votes") ?></a></th>
-					<th><a href="?<?= mkurl('SB=p&SO=' . $SO_next) ?>"><?= __("Popularity") ?></a></th>
+					<th><a href="?<?= mkurl('SB=p&SO=' . $SO_next) ?>"><?= __("Popularity") ?></a><span title="<?= __('Popularity is calculated as the sum of all votes with each vote being weighted with a factor of 0.98 per day since its creation.') ?>" class="hover-help"><sup>?</sup></span></th>
 					<?php if ($SID): ?>
 					<th><a href="?<?= mkurl('SB=w&SO=' . $SO_next) ?>"><?= __("Voted") ?></a></th>
 					<th><a href="?<?= mkurl('SB=o&SO=' . $SO_next) ?>"><?= __("Notify") ?></a></th>