docs: 📚️ input names are not case-sensitive

Author: bubkoo

README.md

@@ -78,6 +78,8 @@ jobs:
 
 ### Inputs
 
+> Note: [Workflow command and parameter names are not case-sensitive](https://docs.github.com/en/free-pro-team@latest/actions/reference/workflow-commands-for-github-actions#about-workflow-commands).
+
 - `app_id`: The ID of the GitHub App. [Create an secret](https://help.github.com/en/actions/configuring-and-managing-workflows/creating-and-storing-encrypted-secrets#creating-encrypted-secrets-for-a-repository) named `'APP_ID'` to store your app ID, then used by `${{ secrets.APP_ID }}`
 - `private_key`: The private key of the GitHub App (can be Base64 encoded). [Create an secret](https://help.github.com/en/actions/configuring-and-managing-workflows/creating-and-storing-encrypted-secrets#creating-encrypted-secrets-for-a-repository) named `'PRIVATE_KEY'` to store your app private key, then used by `${{ secrets.APP_ID }}`
 - `variable_name`: The name of generated token in exported variable. Specify a varable name will set an environment variable with specfiied name and valued with generated token, and can be use in next step with `${ private_key }`.