update docs

Author: DenisaCG

README.md

@@ -36,9 +36,9 @@ for example: `~/.jupyter/jupyter_notebook_config.py`, and specify your long-term
 ```python
 c = get_config()
 
-c.DrivesConfig.access_key_id = "<AWS Access Key ID / IAM Access Key ID>"
-c.DrivesConfig.secret_access_key = "<AWS Secret Access Key / IAM Secret>"
-c.DrivesConfig.session_token = "<AWS Session Token / IAM Session Token>"
+c.DrivesConfig.access_key_id = "<Drives Access Key ID / IAM Access Key ID>"
+c.DrivesConfig.secret_access_key = "<Drives Secret Access Key / IAM Secret>"
+c.DrivesConfig.session_token = "<Drives Session Token / IAM Session Token>"
 ```
 
 ### Custom credentials file path
@@ -51,13 +51,25 @@ c = get_config()
 c.DrivesConfig.custom_credentials_path = "path/to/file/containing/credentials"
 ```
 
+### Environment variables
+
+The credentials can also be set through environment variables that will be automatically extracted.
+
+````bash
+export JP_DRIVES_PROVIDER="<Drives provider e.g.: s3, gcs>"
+export JP_DRIVES_ACCESS_KEY_ID="<Drives Access Key ID>"
+export JP_DRIVES_SECRET_ACCESS_KEY="<Drives Secret Access Key>"
+export JP_DRIVES_SESSION_TOKEN="<Drives Session Token (optional)>"
+export JP_DRIVES_CUSTOM_CREDENTIALS_PATH="<Path to local file which contains credentials (optional)>"
+
+
 ## Uninstall
 
 To remove the extension, execute:
 
 ```bash
 pip uninstall jupyter_drives
-```
+````
 
 ## Troubleshoot