* jpg and png ocr

* fix

* write docs to tmp file

* fix

* [BUGFIX] local_doc_qa.py line 172: logging have no end args. (#323)

* image loader

* fix

* fix

* update api.py

* update api.py

* update api.py

* update README.md

* update api.py

* add pdf_loader

* fix

---------

Co-authored-by: RainGather <3255329+RainGather@users.noreply.github.com>
Co-authored-by: imClumsyPanda <littlepanda0716@gmail.com>