readme: document -o parameters in configuration section

README.md

@@ -129,6 +129,9 @@ Each module can use each of the parameters above, but can also declare their
 own. You can find in each module's documentation page the parameters that they
 are using.
 
+Configuration parameters can be overwritten using the `-o/--option` arguments,
+as described in the [Usage](#tool) section.
+
 It is also possible to set a parameters dynamically, using the `set` command.
 This configuration is only available during the current interactive session,
 and also gets cleaned up when an instance is switched.