feat: consolidate all feeds into a single template and normalize inputs

src/feeds/feed.liquid

@@ -1,23 +0,0 @@
----
-layout: null
-permalink: /feeds/posts
----
-{% layout "./_includes/feeds/feed.liquid" %}
-{% block title %}All posts • Cory Dransfeldt{% endblock %}
-{% block self %}feed.xml{% endblock %}
-{% block update %}
-  {{ collections.posts[0].date | date: "%Y-%m-%dT%H:%M:%S-08:00" }}{% endblock %}
-{% block entries %}
-  {% assign posts = collections.posts | reverse %}
-  {% for post in posts limit: 15 %}
-    <entry>
-      <title>{{ post.data.title }}</title>
-      <link href="{{ site.url }}{{ post.url }}" />
-      <updated>{{ post.date | date: "%m.%d.%Y" }}</updated>
-      <id>{{ site.url }}{{ post.url }}</id>
-      <content type="html">
-        {{ post.data.post_excerpt | markdown | escape }}
-      </content>
-    </entry>
-  {% endfor %}
-{% endblock %}