add troubleshooting section to readme

Author: bradlc

README.md

@@ -85,3 +85,11 @@ Unknown or invalid path used with the [`theme` helper](https://tailwindcss.com/d
 #### `tailwindCSS.lint.cssConflict`
 
 Class names on the same HTML element which apply the same CSS property or properties. **Default: `warning`**
+
+## Troubleshooting
+
+If you’re having issues getting the IntelliSense features to activate, there are a few things you can check:
+
+- Ensure that you have a Tailwind config file in your workspace and that this is named `tailwind.config.js` or `tailwind.js`. Check out the Tailwind documentation for details on [creating a config file](https://tailwindcss.com/docs/installation/#3-create-your-tailwind-config-file-optional).
+- Ensure that the `tailwindcss` module is installed in your workspace, via `npm`, `yarn`, or `pnpm`. Tailwind CSS IntelliSense does not currently support Yarn Plug'n'Play.
+- If you installed `tailwindcss` or created your config file while your project was already open in Visual Studio Code you may need to reload the editor. You can either restart VS Code entirely, or use the `Developer: Reload Window` command which can be found in the command palette.