[Feature Request] Option to export "notes" as TXT files next to the PDF in document_exporter

Description Hello, I have been thinking I should start to use notes (mostly for receipt for stuff I buy in other currencies, to know how much I paid at the time of the receipt in my own currency) however something is kinda stopping me from using it... I am exporting my data with document_exporter multiple times a day for backup purposes (one of the best feature of Paperless! Thank you!), however, after trying to use notes, I noticed that in the exports they are only stored in the manifest.json files... and tied to a document ID. It would be really nice to have them exported as a .txt (or .md) directly next to the PDF they're associated with (and with the same name), that way the export becomes "complete". Having them all in the same file would be fine, otherwise just a XX-2.txt and XX-3.txt ... for each note would be fine. Other PS: A massive thank you for your work on Paperless-NGX, this is one of the most important and useful software I use, thank you …