Add Docling in the benchmark

[hongbo-miao]

I know MinerU is doing better job than Docling today after I compare the results already.
However, it would be great to add https://github.com/DS4SD/docling in the benchmark : )

[ouyanglinke]

Certainly! We will gradually add model evaluation results soon. If you already have inference results from your models, feel free to share them with us.

[hongbo-miao]

@ouyanglinke oh Docling cannot recognize formulas, whereas MinerU handles them nearly perfectly. This alone is already a huge win. ☺️