move envs to new format

docs/markdown/backend/available.md

@@ -20,6 +20,7 @@ backends:
   name-of-backend:
     type: b2
     path: 'myAccount:myBucket/my/path'
+    env:
       B2_ACCOUNT_ID: backblaze_account_id
       B2_ACCOUNT_KEY: backblaze_account_key
 ```
@@ -33,6 +34,7 @@ backends:
     path: s3.amazonaws.com/bucket_name
     # Minio
     # path: http://localhost:9000/bucket_name
+    env:
       AWS_ACCESS_KEY_ID: my_key
       AWS_SECRET_ACCESS_KEY: my_secret
 ```