add gls area prefix

glossary.tex

@@ -10,6 +10,7 @@
 
 \newglossaryentry{area}{
   name={Area},
+  prefix={an\space},
   description={The basic unit of large spaces. An area is a space made distinct by its features. In a dungeon, each room might count as an area, while out in the open plains a forest might be composed of the local areas: `the centre with the big, felled tree; the river's fork; the priestess's house and the griffins' nesting site}
   }