[idea] adding settings to enable/disable image files ocr

[uiharu-s]

Now, ocr on PDFs is optional. It'd be nice if operations on JPEGs are also optional.

Why: be consistent and let users choose file types to be ocr'ed

My use-case: Some users tend to upload a lot of photos, which take up significant resource to ocr, while the number of scanned documents are fewer than the photos, they are arguably more useful to be ocr'ed and searchable.

[keslerm]

I can add this in i think and create a PR, I need the same thing.