Mutator example in readme lacks injection point.

I think the second code block under "Using external mutator to produce test cases" in the readme is incorrect.

The example does not include a FUZZ injection point:

# Generate 1000 example payloads
radamsa -n 1000 -o %n.txt example1.txt example2.txt

# This results into files 1.txt ... 1000.txt
# Now we can just read the payload data in a loop from file for ffuf

ffuf --input-cmd 'cat $FFUF_NUM.txt' -H "Content-Type: application/json" -X POST -u https://ffuf.io.fi/ -mc all -fc 400

Ideally I would think the example would read like: ffuf --input-cmd 'cat $FFUF_NUM.txt' -H "Content-Type: application/json" -X POST -u https://ffuf.io.fi/FUZZ -mc all -fc 400

OR

ffuf --input-cmd 'cat $FFUF_NUM.txt' -H "Content-Type: application/json" -X POST -d "FUZZ" -u https://ffuf.io.fi/ -mc all -fc 400

Hopefully I am not drastically misunderstanding the usage here?