update docs

[Erich-e]

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Hi, and thank you for this project

I tried running this sample shortcut relationship filter against the example api, but I ran into a problem that looks like GET /persons?filter=[{"name":"computers__serial","op":"ilike","val":"%Amstrad%"}] HTTP/1.1

127.0.0.1 - - [24/Sep/2021 00:18:58] "GET /persons?filter=%5B%7B%22name%22%3A+%22computers__serial%22%2C+%22op%22%3A+%22ilike%22%2C+%22val%22%3A+%22%25Amstrad%25%22%7D%5D HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/Users/erich/.pyenv/versions/3.9.4/envs/frj/lib/python3.9/site-packages/flask/app.py", line 2088, in __call__
    return self.wsgi_app(environ, start_response)
 . . . 
  File "/Users/erich/.pyenv/versions/3.9.4/envs/frj/lib/python3.9/site-packages/flask_rest_jsonapi/data_layers/filtering/alchemy.py", line 20, in create_filters
    filters.append(Node(model, filter_, resource, resource.schema).resolve())
  File "/Users/erich/.pyenv/versions/3.9.4/envs/frj/lib/python3.9/site-packages/flask_rest_jsonapi/data_layers/filtering/alchemy.py", line 53, in resolve
    return getattr(self.column, self.operator)(**value)
TypeError: ilike() got an unexpected keyword argument 'serial'

It looks like this is because the filter ultimately is becoming Computer.ilike(serial="%Amstrad%"). So this is to update the example to a filter that becomes Computer.any(serial="Amstrad")