Update readme to contain full usage info

README.md

@@ -1,6 +1,11 @@
 # inngest/setup-inngest
 
-This action installs the Inngest CLI ([inngest/inngest](https://github.com/inngest/inngest))
+This action installs the Inngest CLI ([inngest/inngest](https://github.com/inngest/inngest)) on your Linux, Mac, or Windows runner in GitHub Actions.
+
+You probably want to use a more specific action that uses this internally - see:
+
+- [inngest/action-deploy-functions](https://github.com/inngest/action-deploy-functions)
+- [inngest/action-test-functions](https://github.com/inngest/action-test-functions)
 
 ## Usage
 
@@ -10,6 +15,9 @@ steps:
   - uses: inngest/setup-inngest@v1
     with:
       version: 0.5.2
+      key: ${{ secrets.INNGEST_API_KEY }}
 ```
 
-The `version` input is optional. If not supplied, the latest version will be used.
+The `version` input is optional. If not supplied, the `"latest"` version will be used.
+
+The `key` input is also optional. If supplied, we'll log in to the CLI for you (synonymous with using `inngest login --token [key]`). This is useful if you wish to perform authenticated commands with the CLI, like [deploying functions](https://github.com/inngest/action-deploy-functions) or [testing against production data](https://github.com/inngest/action-test-functions).