Update README.md

README.md

@@ -5,7 +5,7 @@ massively because the bloomfilter can, even just given one word, reduce the
 number of files that need to be searched by around 97-99%.
 
 In this context, "word"
-means something that matches [a-zA-Z_] but is not surrounded by one of
+means something that matches `[a-zA-Z_]` but is not surrounded by one of
 those characters (see `make_bloom_from_file` in `common.c` if this sounds
 too complicated.)