Add an app for paperless-ngx

[maxime1992]

https://docs.paperless-ngx.com is in my top 3 of apps to self host.

Compared to some apps that have a non open source equivalent at least, I don't think I've ever used an app that comes anywhere near paperless-ngx.

It'd be fantastic if you could add support for it :pray:!

Thanks

[highghlow]

I have started working on this request

[highghlow]

It's done

[nmfretz]

Paperless-ngx is now available in the app store thanks to @highghlow! Closed by https://github.com/getumbrel/umbrel-apps/commit/3cb4c100c1a428629680d53d2e479c1e04e73d8d.