Refactor app in to its own slice

slices/main/templates/blogroll/opml.xml.builder

@@ -0,0 +1,16 @@
+# xml.instruct! "xml-stylesheet", {href: "/assets/style.xslt", type: "text/xsl"}
+xml.opml("xmlns:frss" => "https://freshrss.org/opml", version: "2.0") do
+  xml.head do |head|
+    head.title "Daniel Nitsikopoulos's RSS subscriptions"
+    head.link "https://dnitza.com/blogroll/opml"
+    head.lastBuildDate Time.now.rfc2822
+    head.pubDate Time.now.rfc2822
+    head.ttl 1800
+  end
+
+  xml.body do
+    blogroll.each do |blog|
+      xml.outline(text: blog[:title], type: "rss", xmlUrl: blog[:url], htmlUrl: blog[:html_url])
+    end
+  end
+end