userguide: Add rule file globbing option details

Signed-off-by: jason taylor <jtfas90@gmail.com>

doc/userguide/partials/options.rst

@@ -92,11 +92,17 @@
    With the -s option you can set a file with signatures, which will
    be loaded together with the rules set in the yaml.
 
+   It is possible to use globbing when specifying rules files.
+   For example, ``-s '/path/to/rules/*.rules'``
+
 .. option:: -S <filename.rules>
 
    With the -S option you can set a file with signatures, which will
    be loaded exclusively, regardless of the rules set in the yaml.
 
+   It is possible to use globbing when specifying rules files.
+   For example, ``-S '/path/to/rules/*.rules'``
+
 .. option:: -l <directory>
 
    With the -l option you can set the default log directory. If you