Update docs to include response_format for OpenAI ChatTextGenerator; responseFormat is supported but not documented

[mrprkr]

type OpenAIChatSettings is missing option for response_format

Example:

      .ChatTextGenerator({
        model: 'gpt-4-vision-preview',
        maxGenerationTokens: 2048,
        temperature: 0,
        response_format: { type: "json_object" },
      })
      .withInstructionPrompt(),

[mrprkr]

adding responseFormat is only supported on gpt-4, which throws an error expected an object but received string on vision prompts