[Add]: koreader-sync-server

[jamesrchen]

Short description of the app

Users of koreader devices can register their devices to the synchronization server and use the sync service to keep all reading progress synchronized between devices.

KOReader itself is a document viewer primarily aimed at e-ink readers.

Sources

https://github.com/koreader/koreader-sync-server https://hub.docker.com/r/koreader/kosync

I've read and agree with the following

• [X] I've checked all open and closed issues and my request is not there.
• [X] I've checked all open and closed pull requests and my request is not there.