Document new munge option.

config/vufind/searchspecs.yaml

@@ -145,6 +145,7 @@
 # [preg_replace, pattern, replacement] - Perform a regular expression replace
 #     using the preg_replace() PHP function.  If you use backreferences in your
 #     replacement phrase, be sure to escape dollar signs (i.e. \$1, not $1).
+# [ucfirst] - Uppercase the first letter of each word in the string
 # [uppercase] - Convert string to uppercase
 #
 # See the CallNumber search below for an example of custom munging in action.