Added tag filtering and RSS feed

posts/feed.php

@@ -0,0 +1,41 @@
+<?php
+require __DIR__ . '/posts.php';
+
+$siteUrl   = 'https://hexstudios.co';
+$siteTitle = 'Hex Studios';
+$siteDesc  = 'Developer, biker, musician, engineer, and an unapologetic centrist in the deep red south.';
+
+$posts = getPosts(__DIR__);
+
+function xmlEscape($str) {
+    return htmlspecialchars($str, ENT_XML1 | ENT_QUOTES, 'UTF-8');
+}
+
+header('Content-Type: application/rss+xml; charset=UTF-8');
+echo '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
+?>
+<rss version="2.0">
+    <channel>
+        <title><?= xmlEscape($siteTitle) ?></title>
+        <link><?= xmlEscape($siteUrl) ?></link>
+        <description><?= xmlEscape($siteDesc) ?></description>
+        <language>en-us</language>
+        <lastBuildDate><?= date(DATE_RSS) ?></lastBuildDate>
+        <?php foreach ($posts as $post):
+            $postUrl = $post['type'] === 'html'
+                ? $siteUrl . '/posts/' . $post['file']
+                : $siteUrl . '/post.html?file=' . urlencode($post['file']);
+        ?>
+        <item>
+            <title><?= xmlEscape($post['title']) ?></title>
+            <link><?= xmlEscape($postUrl) ?></link>
+            <guid isPermaLink="true"><?= xmlEscape($postUrl) ?></guid>
+            <pubDate><?= date(DATE_RSS, $post['created']) ?></pubDate>
+            <description><?= xmlEscape($post['excerpt']) ?></description>
+            <?php foreach ($post['tags'] as $tag): ?>
+                <category><?= xmlEscape($tag) ?></category>
+            <?php endforeach; ?>
+        </item>
+        <?php endforeach; ?>
+    </channel>
+</rss>