Update readme.md (#32)

Added some information for AWS Lambda usage. Came across the permissions like described.

readme.md

@@ -17,6 +17,11 @@ You can use laravel's default `\Log` class to use this
 
 `\Log::info('user logged in', ['id' => 123, 'name' => 'Naren']);`
 
+### Usage with AWS Lambda
+
+Make sure the AWS Lambda template contains an IAM role with enough access.
+So think about Logs:CreateLogGroup, Logs:DescribeLogGroups, Logs:CreateLogStream, Logs:DescribeLogStream, Logs:PutRetentionPolicy and Logs:PutLogEvents
+
 ### Config
 
 Config for logging is defined at `config/logging.php`. Add `cloudwatch` to the `channels` array