Make appcast h1 underline padded better

What's New page's CSS already has this padding but I forgot to add it to
appcast styles.

Author: ychin

appcast/_appcast_style.css

@@ -1,4 +1,4 @@
 <style>
 :root { supported-color-schemes: light dark; color-scheme: light dark; }
-h1 { border-bottom: 1px solid gray; }
+h1 { padding-bottom: .3em; border-bottom: 1px solid gray; }
 </style>