Bump version to v0.21.4

Author: github-actions[bot]

index.html

@@ -528,7 +528,7 @@
 <!-- ═══ NAV ═══ -->
 <nav class="nav">
   <div class="nav-inner">
-    <a href="#" class="brand"><span class="brand-mark">▸</span>dirge<span class="brand-ver">v0.21.3</span></a>
+    <a href="#" class="brand"><span class="brand-mark">▸</span>dirge<span class="brand-ver">v0.21.4</span></a>
     <div class="nav-links">
       <a href="#features">Features</a>
       <a href="#install">Install</a>