Add vision capability (#2025)

* Add vision capability

* Configurate: description_prompt

* Print warning instead of raising issues for type

* Skip vision capability test if dependencies not installed

* Append "vision" to agent's system message when enabled VisionCapability

* GPT-4V notebook update with ConversableAgent

* Clean GPT-4V notebook

* Add vision capability test to workflow

* Lint import

* Update system message for vision capability

* Add a `custom_caption_func` to VisionCapability

* Add custom function example for vision capability

* Skip test Vision capability custom func

* GPT-4V notebook metadata to website

* Remove redundant files

* The custom caption function takes more inputs now

* Add a more complex example of custom caption func

* Remove trailing space

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Co-authored-by: Chi Wang <wang.chi@microsoft.com>