Document how to configure which model to use

Author: artyom

README.md

@@ -18,7 +18,8 @@ llmcli -h
 
 ## Requirements
 
-- AWS account with Bedrock access and the following models enabled: Anthropic Claude 3.5 Sonnet, Anthropic Claude 3 Sonnet.
+- AWS account with Bedrock access and at least one [model that supports ConverseStream API and system prompt](https://docs.aws.amazon.com/bedrock/latest/userguide/conversation-inference-supported-models-features.html) enabled.
+  Configure which model to use with `LLMCLI_MODEL` environment variable (example: `us.amazon.nova-micro-v1:0`).
 - Properly configured AWS credentials.
   This tool tries to use AWS profile named “llmcli”, and falls back to default AWS credentials if profile is not found.