feat: add option to use JPEG compression

[Krifto]

With the default setup, scanned pages take multiple megabytes. The newly added USE_JPEG_COMPRESSION environment variable enables JEPG compression (quality factor 80), significantly reducing file sizes.

see https://codeyarns.com/tech/2010-04-12-graphicsmagick-compression-methods.html

[PhilippMundhenk]

Thank you for the contribution! Love it! Did happen to have tested this with OCR? I wonder if this impacts OCR quality, if not this could even be enabled by default

[Krifto]

Thanks for incorporating! I have not tried OCR, since I do all the OCR in paperless-ngx. But that also just uses Tesseract, and I have been feeding that with 300 resolution and JPEG quality 80 for about a year now without any issues.

A further idea could be to also expose the graphicsmagic's quality setting via envronment variable, which controls the amount of compression. But that would take some parameter sanitizing (clamp values to 0-100), and that is beyond my shell script skills :)