Integrate Mistral OCR and MinerU in SiYuan

Hello Mistral OCR is a good (and cheap, I haven't been able to go beyond free use in several months) solution for convert .pdf to .md format.

I mainly use SiYuan as a tool that is as convenient as possible for editing .md from .pdf thanks to multi-window mode.

In my opinion, integrating Mistral OCR and other projects like MinerU into SiYuan will greatly improve user performance.