add documentation reference

README.md

@@ -2,6 +2,12 @@
 
 **openfsd** is an open-source multiplayer flight simulation server implementing the modern VATSIM FSD protocol. It connects pilots and air traffic controllers in a shared virtual environment.
 
+## About
+
+Flight Sim Daemon (colloquially known as FSD) is the software/protocol responsible for connecting home flight simulator clients to a single, shared multiplayer world on hobbyist networks such as [VATSIM](https://vatsim.net/docs/about/about-vatsim) and [IVAO](https://www.ivao.aero/).
+FSD was originally written in the late 90's by [Marty Bochane](https://github.com/kuroneko/fsd) for [SATCO](https://web.archive.org/web/20000619145015/http://www.satco.org/), later to be forked and taken closed-source by VATSIM in 2001.
+As of May 2025, FSD is still used to facilitate over 140,000 active members connecting their flight simulators to the [network](https://vatsim-radar.com/).
+
 ## Features
 
 - Facilitate multiplayer flight simulation with VATSIM protocol compatibility.
@@ -43,3 +49,14 @@ The preferred way to run openfsd is using **Docker** and **Docker Compose**. See
 ## API
 
 The web server exposes APIs under `/api/v1` for authentication, user management, and configuration. Although a basic web interface is provided, users are encouraged to call this API from their own external applications. See the [API](https://github.com/renorris/openfsd/tree/main/web) documentation.
+
+## Docs
+
+Unofficial reverse-engineered protocol documentation is included in this repository:
+
+```
+pip install mkdocs
+git clone git@github.com:renorris/openfsd.git
+cd openfsd/
+mkdocs serve
+```