Add documentation

Author: jonathanrainer

docs/source/commands/supergraphs.mdx

@@ -229,3 +229,16 @@ We recommend updating to the latest version of Rover as soon as possible. If you
 |---|---|
 |<= v0.2.x|<= v0.38.x|
 |>= v0.3.x|>= v0.39.x|
+
+## Printing the JSON Schema for use with Editor Validation
+
+### `supergraph print-json-schema`
+
+You can use Rover to print the JSON Schema for the `supergraph.yaml` file to the console or to a file, like so
+
+```bash
+rover supergraph print-json-schema
+```
+
+This can then be consumed by an IDE to allow for automatic checking of the structure of the `supergraph.yaml` file. For
+example, you can use in VSCode by following the instructions [here](https://code.visualstudio.com/docs/languages/json#_json-schemas-and-settings)