release: update appcast for v1.8.4

Author: JerryZLiu

docs/appcast.xml

@@ -3,6 +3,18 @@
   <channel>
     <title>Dayflow Updates</title>
     <language>en</language>
+    <item>
+      <title>Version 1.8.4</title>
+      <pubDate>Wed, 04 Mar 2026 11:17:53 +0000</pubDate>
+      <enclosure url="https://github.com/JerryZLiu/Dayflow/releases/download/v1.8.4/Dayflow.dmg"
+                 sparkle:version="95"
+                 sparkle:shortVersionString="1.8.4"
+                 length="37644715"
+                 type="application/octet-stream"
+                 sparkle:edSignature="9W9ZBS+91G8Kwz6mHsxU0ZiyODnH2hLBitHalrvaU/zaI26Owfb+k6V5oGsPBFtUkBwKoKMaGFWECHk2dxHmBw=="/>
+      <sparkle:minimumSystemVersion>13.0</sparkle:minimumSystemVersion>
+      <releaseNotesLink>https://github.com/JerryZLiu/Dayflow/releases/tag/v1.8.4</releaseNotesLink>
+    </item>
     <item>
       <title>Version 1.8.3</title>
       <pubDate>Mon, 02 Mar 2026 09:35:35 +0000</pubDate>