Support Async LLM Client, reuse llm_caption helper

[hlohaus]

Example Code:

import asyncio
from g4f.client import AsyncClient
from markitdown import MarkItDown

import g4f.debug
g4f.debug.logging = True

async def main():
    client = AsyncClient()
    md = MarkItDown(
        llm_client=client,
        llm_model="PollinationsAI:openai",
    )

    print(await (md.convert(open("waterfall.jpeg", "rb")).text_content))

asyncio.run(main())

[hlohaus]

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