Add documentation on log level

doc/README.md

@@ -12,6 +12,24 @@ When a crash occurs in driftctl, we do not send any crash reports.
 For debugging purposes, you can add `--error-reporting` when running driftctl and crash data will be sent to us via [Sentry](https://sentry.io)
 Details of reported data can be found [here](./cmd/flags/error-reporting.md)
 
+#### Log level
+
+By default driftctl logger only display warning and error messages. You can set `LOG_LEVEL` environment variable to change the default level.
+Valid values are : trace,debug,info,warn,error,fatal,panic.
+
+**Note:** In trace level, terraform provider logs will be shown.
+
+Example
+
+```shell
+LOG_LEVEL=debug driftctl scan
+DEBU[0000] New provider library created
+DEBU[0000] Found existing provider path=/home/driftctl/.driftctl/plugins/linux_amd64/terraform-provider-aws_v3.19.0_x5
+DEBU[0000] Starting gRPC client alias=us-east-1
+DEBU[0001] New gRPC client started alias=us-east-1
+...
+```
+
 ### Usage
 
 - Commands
@@ -24,4 +42,4 @@ Details of reported data can be found [here](./cmd/flags/error-reporting.md)
 
 ## Issues
 
-- [Known Issues & Limitations](LIMITATIONS.md)
+- [Known Issues & Limitations](LIMITATIONS.md)