add ending separator, update headers level

src/view/post.gemini

@@ -1,6 +1,6 @@
-## {author}
+### {author}
 {quote}
 {message}
 ```
 {time} #{txid}
-```
+```

src/view/posts.gemini

@@ -2,4 +2,6 @@
 
 # {subject}
 
+## Posts
+
 {posts}