Add documentation for LotATC export plugin

Lua-Plugins.md

@@ -67,6 +67,39 @@ These scripts add a lot of runtime functionalities :
 You can find the *VEAF Framework* plugin [on GitHub](https://github.com/VEAF/dcs-liberation-veaf-framework/releases)
 For more information, please visit the [VEAF Framework documentation site](https://veaf.github.io/VEAF-Mission-Creation-Tools/) (work in progress)
 
+### The *LotATC export* plugin
+
+This plugin can export [LotATC](https://www.lotatc.com/) compatible drawings of threat circles of SAMS and AAA for Blue and Red coalition. These threat circles reflect the campaign state and are generated once during mission start. Once a GCI connects with the LotATC client to the server that hosts the mission, these drawings are auto loaded in the LotATC client and displayed.
+
+To make auto loading work correctly, the computer that hosts the DCS server needs some small setup.
+
+#### DCS server setup
+
+The lua script as plugin that generates the drawings runs exactly once during mission startup. This script generates the JSON for the selected faction, RED or BLUE or both, to the output folder specified by the environment variable `LOTATC_DRAWINGS_DIR`.
+
+On the server machine the `LOTATC_DRAWINGS_DIR` should be set to:
+
+* LotATC 2.2+: `C:\users\<you>\LotAtc Data\Server\drawings\`
+* LotATC <2.2: `C:\users\<you>\Saved Games\DCS(instance)\Mods\services\LotAtc\userdb\drawings\`
+
+For LotATC 2.2+ both are accepted but the first is recommended.
+
+#### Local generation
+
+For local generation of the drawings it is enough to generate the "next turn" by pressing "Take Off", load the .miz file in DCS and quit again. The drawings are generated either to the path of `LOTATC_DRAWINGS_DIR` or as fallback to `Saved Games\DCS(instance)\Mods\services\LotAtc\userdb\drawings\`. These drawings can then be manually loaded in the LotATC client.
+
+#### NATO names
+
+The names generated for a SAM site always include the group name from the campaign. E.g. for the SA-10 site "LYNX" the generated LotATC label will contain `LYNX|SAM`. By default it is not possible to generate the threat type because a SAM group consist of many different units and there is no one that is called "SA-10". But the exporter can infer the NATO name of the threat site with `SKYNET`. So if the `SKYNET` is active in the options it is very likely that the LotATC label will be `LYNX|SAM|SA-10`.
+
+#### Plugin options
+
+The plugin can be configured to control the exported drawings.
+
+* Export RED AA - will export threat circles for the RED faction. These are loaded if a BLUE GCI connects to LotATC.
+* Export BLUE AA - will export threat circles for the BLUE faction. These are loaded if a RED GCI connects to LotATC.
+* Export AA Symbols - will additional export a classification symbol for every AA threat that marks the center of the site.
+
 ## Custom plugins
 
 The easiest way to create a custom plugin is to copy an existing plugin, and modify the files.