chore(*): add code style section to doc

CONTRIBUTING.md

@@ -2,6 +2,23 @@
 
 Contributions to SASjs are very welcome! When making a PR, test cases should be included.
 
+## Code Style
+
+This repository uses `Prettier` to ensure a uniform code style.
+If you are using VS Code for development, you can automatically fix your code to match the style as follows:
+
+- Install the `Prettier` extension for VS Code.
+- Open your `settings.json` file by choosing 'Preferences: Open Settings (JSON)' from the command palette.
+- Add the following items to the JSON.
+  ```
+    "editor.formatOnSave": true,
+    "editor.formatOnPaste": true,
+  ```
+
+If you are using another editor, or are unable to install the extension, you can run `npm run lint:fix` to fix the formatting after you've made your changes.
+
+## Testing
+
 This repository contains a suite of tests built using [@sasjs/test-framework](https://github.com/sasjs/test-framework).
 
 Detailed instructions for creating and running the tests can be found [here](https://github.com/sasjs/adapter/blob/master/sasjs-tests/README.md).