Allow passing pdf bytes and return string

[fluqc]

Requested feature

Allow passing PDF bytes directly to the converter and return the extracted Markdown as a string.

Alternatives

Currently, users must write PDFs to disk before conversion, which adds unnecessary I/O overhead and complexity .

[hnc-leebd]

@MaximPlusov
Could you please review whether the development of this feature is possible?

[MaximPlusov]

@hnc-leebd The development of this feature is possible, we can plan it.