Add compilation instructions.

README.md

@@ -6,6 +6,10 @@ Usage:
 
 The API/Schema for the input json file will soon be documented.
 
+# Compilation
+This project uses git submodules. So before compiling, please ensure you have cloned them (either by doing `git clone --recursive https://github.com/randovania/YAMS`, or if you have already cloned the repo, `git submodule update --init`).  
+After that, you can use the standard dotnet compilation step: `dotnet build YAMS-CLI`.
+
 # License
 All code is licensed under the GNU Public License version 3. See the `LICENSE-CODE` file for full details.  
 Art assets are licensed under [CC-BY-SA 4.0](https://creativecommons.org/licenses/by/4.0/). For the full list of authors and more details, please read the `Attribution.md` file located in [`YAMS-LIB/sprites/`](./YAMS-LIB/sprites/Attribution.md).