fix: package description on /packages/{name} view

...What in the world happened here. We were literally just populating
`pkg` based on `pkgbase.packages.first()`. We should have been focusing
on the package passed by the context, which is always available when
`show_package_details` is true.

Closes #384

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/partials/packages/details.html

-{% set pkg = pkgbase.packages.first() %}
 <table id="pkginfo">
     <tr>
         <th>{{ "Git Clone URL" | tr }}:</th>
@@ -20,13 +19,13 @@
         </tr>
         <tr>
             <th>{{ "Description" | tr }}:</th>
-            <td class="wrap">{{ pkg.Description }}</td>
+            <td class="wrap">{{ package.Description }}</td>
         </tr>
         <tr>
             <th>{{ "Upstream URL" | tr }}:</th>
             <td class="wrap">
-                {% if pkg.URL %}
-                    <a href="{{ pkg.URL }}">{{ pkg.URL }}</a>
+                {% if package.URL %}
+                    <a href="{{ package.URL }}">{{ package.URL }}</a>
                 {% else %}
                     {{ "None" | tr }}
                 {% endif %}