Update phpmailer_arg_injection.md

Added options to the module docs for the new options

Author: erikbomb

documentation/modules/exploit/multi/http/phpmailer_arg_injection.md

@@ -18,6 +18,17 @@ exploitation can take a few minutes.
   6.  Verify the module yields a PHP meterpreter session in < 5 minutes
   7.  Verify the malicious PHP file was automatically removed
 
+## Options
+
+### WaitTimeout
+Seconds to wait to trigger the payload
+### NameField
+Name of the element for the Name field
+### EmailField
+Name of the element for the Email field
+### MessageField
+Name of the element for the Message field
+
 ## Scenarios
 
   Demo taken directly from [PR7768](https://github.com/rapid7/metasploit-framework/pull/7768)