add new cli params to readme

README.md

@@ -52,6 +52,10 @@ $ fail2ban-prometheus-exporter -h
         path to the fail2ban server socket
   -version
         show version info and exit
+   -collector.textfile
+        enable the textfile collector
+  -collector.textfile.directory string
+        directory to read text files with metrics from
 ```
 
 **Example**