docs: Update some documentation to catch up with added options.

docs/CLI.rst

@@ -3,19 +3,24 @@
 
 ::
 
-    usage: pyrasite [-h] [--gdb-prefix GDB_PREFIX] [--verbose] pid [filename]
+    usage: pyrasite [-h] [--gdb-prefix GDB_PREFIX] [--verbose] pid [filepath|payloadname]
+           pyrasite --list-payloads
 
     pyrasite - inject code into a running python process
 
     positional arguments:
       pid                   The ID of the process to inject code into
-      filename              The second argument must be a filename
+      filepath|payloadname  The second argument must be a path to a
+                            file that will be sent as a payload to the
+                            target process or it must be the name of
+                            an existing payload (see --list-payloads).
 
     optional arguments:
       -h, --help            show this help message and exit
       --gdb-prefix GDB_PREFIX
                             GDB prefix (if specified during installation)
       --verbose             Verbose mode
+      --list-payloads       List payloads that are delivered by pyrasite
 
     For updates, visit https://github.com/lmacken/pyrasite