firefox: add aur search shortcut

hosts/common/programs/firefox/bookmarks.html

@@ -9,6 +9,7 @@
   <dt><h3 unfiled_bookmarks_folder="true">Other Bookmarks</h3>
   <dl><p>
     <!-- XXX: if you want multiple aliases, declare the link twice WITH A DIFFERENT HREF= else firefox dedupes them (case-insensitively) -->
+    <dt><a href="https://aur.archlinux.org/packages?O=0&K=%s" shortcuturl="aur">Search AUR
     <dt><a href="https://docs.rs/releases/search?query=%s" shortcuturl="docsrs">Search docs.rs
     <dt><a href="https://duckduckgo.com/?t=h_&q=%s" shortcuturl="ddg">Search DuckDuckGo
     <dt><a href="https://en.wikipedia.org/wiki/Special:Search?search=%s" shortcuturl="w">Search Wikipedia