Use yyyy-mm-dd as date for PDF extraction

Would it be possible to format the date as yyyy-mm-dd?

zotfile/chrome/content/zotfile/pdfAnnotations.js

Line 233 in 5540f52

    
           var date_str = this.getPref("pdfExtraction.localeDateInNote") ? new Date().toLocaleString() : new Date().toUTCString(),

I can open a PR with the changes, but I'd like to ask what would be the preferred way to handle the preferences:

zotfile/defaults/preferences/defaults.js

Line 130 in 5540f52

pref("extensions.zotfile.pdfExtraction.localeDateInNote", true);

Would substituting the existing preference for a string-based one, and substituting the ternary operator above for a switch case be alright?

// where predefined_options can be any of 'locale', 'utc' 'ISO' or 'yyyy-mm-dd' 
pref("extensions.zotfile.pdfExtraction.dateFormat", "<predefined_options>");

Or would it be best to pass a different wildcard here, such as {'title': str_title, 'date': date_str, 'isodate': iso_date}:
`

zotfile/chrome/content/zotfile/pdfAnnotations.js

Line 234 in 5540f52

    
           title = this.Utils.str_format(format_title, {'title': str_title, 'date': date_str}),