post_title should have an outer_tag_class attribute

`post_title` needs to have an `outer_tag_class` attribute. Example:

```django
{% post_title outer_tag="article" outer_tag_class="article-card" link_class="post-title-link" %}
```

Will output:

```django
<article class="article-card">
  <a href="/2025/05/blog-post/" title="My Blog Post Title" class="u-url post-title-link">My Blog Post Title</a>
</article>
```