Add atom user feed

Closes #37

resources/views/atom/user.blade.php

@@ -0,0 +1,41 @@
+<?=
+    /* Using an echo tag here so the `<? ... ?>` won't get parsed as short tags */
+    '<?xml version="1.0" encoding="UTF-8"?>'.PHP_EOL
+?>
+<feed xmlns="http://www.w3.org/2005/Atom" xmlns:thr="http://purl.org/syndication/thread/1.0" xmlns:activity="http://activitystrea.ms/spec/1.0/" xmlns:poco="http://portablecontacts.net/spec/1.0" xmlns:media="http://purl.org/syndication/atommedia" xmlns:ostatus="http://ostatus.org/schema/1.0" xmlns:mastodon="http://mastodon.social/schema/1.0">
+  <id>{{$profile->permalink('.atom')}}</id>
+  <title>{{$profile->username}}</title>
+  <subtitle>{{$profile->bio}}</subtitle>
+  <updated>{{$profile->updated_at->toAtomString()}}</updated>
+  <logo></logo>
+  <author>
+    <id>{{$profile->permalink()}}</id>
+    <activity:object-type>http://activitystrea.ms/schema/1.0/person</activity:object-type>
+    <uri>{{$profile->permalink()}}</uri>
+    <name>{{$profile->permalink()}}</name>
+    <email>{{$profile->emailUrl()}}</email>
+    <summary type="html">{{$profile->bio}}</summary>
+    <link rel="alternate" type="text/html" href="{{$profile->url()}}"/>
+    <link rel="avatar" type="image/jpeg" media:width="120" media:height="120" href="{{$profile->avatarUrl()}}"/>
+    <poco:preferredUsername>{{$profile->username}}</poco:preferredUsername>
+    <poco:displayName>{{$profile->name}}</poco:displayName>
+    <poco:note>{{$profile->bio}}</poco:note>
+    <mastodon:scope>public</mastodon:scope>
+  </author>
+  <link rel="alternate" type="text/html" href="{{$profile->url()}}"/>
+  <link rel="self" type="application/atom+xml" href="{{$profile->permalink('.atom')}}"/>
+@foreach($items as $item)
+    <entry>
+        <title><![CDATA[{{ $item->caption }}]]></title>
+        <link rel="alternate" href="{{ $item->url() }}" />
+        <id>{{ url($item->id) }}</id>
+        <author>
+            <name> <![CDATA[{{ $item->profile->username }}]]></name>
+        </author>
+        <summary type="html">
+            <![CDATA[{!! $item->caption !!}]]>
+        </summary>
+        <updated>{{ $item->updated_at->toAtomString() }}</updated>
+    </entry>
+@endforeach
+</feed>