Update README.md

Author: Peter Appleby

VSCodeExtension/README.md

@@ -10,6 +10,13 @@ This extension is developed independently of Secret Lab Pty Ltd and the Yarn Spi
 
 To learn more about Yarn Spinner, head to the [official site](https://yarnspinner.dev)!
 
+## Importing / Overriding via JSON
+If you want to import command and function definitions for a language other than C#, or you want to override information that the language server parses from C#, add a JSON file with the extension ".ysls.json" to your project's folder using the [ysls.json schema](/LanguageServer/src/Server/Documentation/ysls.schema.json). 
+
+For examples, take a look at this [import example](/LanguageServer/ImportExample.ysls.json) or the [yarn spinner built in Commands and Functions file](/LanguageServer/src/Server/Documentation/BuiltInFunctionsAndCommands.ysls.json). 
+
+One caveat to note; the language server does not automatically reload ysls.json files (nor .cs files). To force the server to reload function and command definitions, go to the extension settings and toggle the "CSharp Lookup" property. (This will be fixed in an upcoming release!)
+
 ## Demo
 <img src="https://user-images.githubusercontent.com/408888/133907128-ab3fe7a3-b2cf-4ce6-98d7-65f048fbae1f.gif" alt="Demonstration of hover tooltip, Go to references, and Go to definition" />