add description for peer-to-peef filesharing category

- https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2984

README.md

@@ -928,6 +928,8 @@ Network distributed filesystems.
 
 **[`^        back to top        ^`](#)**
 
+[Peer-to-peer file sharing](https://en.wikipedia.org/wiki/Peer-to-peer_file_sharing) is the distribution and [sharing](https://en.wikipedia.org/wiki/File_sharing) of digital media using [peer-to-peer](https://en.wikipedia.org/wiki/Peer-to-peer) (P2P) networking technology.
+
 - [bittorrent-tracker](https://webtorrent.io/) - Simple, robust, BitTorrent tracker (client and server) implementation. ([Source Code](https://github.com/webtorrent/bittorrent-tracker)) `MIT` `Nodejs`
 - [cloud-torrent](https://github.com/jpillora/cloud-torrent) - Torrent Web Client with HTTP retrievable or streamable downloaded files. `AGPL-3.0` `Go`
 - [Dat Project](https://datproject.org) - Powerful decentralized file sharing applications built from a large ecosystem of modules. ([Source Code](https://github.com/datproject)) `MIT` `Nodejs`