Add visual question answering to inference client

[martinbrose]

Add visual-question-answering to HuggingFace🤗 Hub

References #1539

This is an ongoing list of model tasks to implement in the Hugging Face Hub inference client. Each task is planned to be its own PR. The task for this is visual-question-answering.

Key Features

• Modifies _client.py to call a visual-question-answering model.
• Modifies documentation to reflect changes.

[Wauplin]

Another great one :) I removed the parameters arg since there is none documented in hf.co/tasks. I adapted the example in the docstring and added a test for it. Looks good to merge :)

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.