Convert PDF to PNG for OCR

[alexk307]

Describe the change
Adds the ability to take a snapshot of the PDF file's first page as a png in order to run OCR on a PDF

Describe testing procedures
Exploded a PDF file and checked the OCR response contained the text.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of and tested my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[phutelmyer]

@alexk307 This is a great idea - had no clue about get_page_pixmap. There's probably not much value in adding in the ability convert additional pages, right?

[alexk307]

This is a great idea - had no clue about get_page_pixmap. There's probably not much value in adding in the ability convert additional pages, right?

Your call! I think for my purposes, it's fine to grab the first page. But we could add another config option in the future to set the max number of pages to scan.