update documentation to show new syntax for creating ollama models with client.create

[indigotechtutorials]

I ran into an issue when I recently updated Ollama and I figured it was an API change. #6
They changed the way that you send parameters for creating models with Ollama and simplified it.
Previously you would need to pass in a complex modelfile string into the client.create

result = client.create(
  { name: 'mario',
    modelfile: "FROM llama2\nSYSTEM You are mario from Super Mario Bros." }
) do |event, raw|
  puts event
end 

Now this is simplified by setting the model, from, and system parameter separately as keys like this

result = client.create(
  { model: 'mario',
    from: 'llama3.2',
    system: 'You are mario from Super Mario Bros.' }
) do |event, raw|
  puts event
end

I updated the docs to show the new syntax of creating ollama models with client.create so hopefully this helps other developers who are using this gem.