chore: add introductory text

Author: Davide Melfi

lambda-runtime/CHANGELOG.md

@@ -7,7 +7,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-## [1.1.1](https://github.com/aws/aws-lambda-rust-runtime/compare/lambda_runtime-v1.1.0-rc1...lambda_runtime-v1.1.1) - 2026-03-11
+## [1.1.1](https://github.com/aws/aws-lambda-rust-runtime/compare/v1.0.2...lambda_runtime-v1.1.1) - 2026-03-11
+
+### Lambda Managed Instances
+
+The runtime now supports Lambda Managed Instances via the `concurrency-tokio` feature flag (previously `experimental-concurrency`). Lambda Managed Instances allow multiple concurrent requests to be processed within a single execution environment. When `AWS_LAMBDA_MAX_CONCURRENCY` is set, the runtime spawns multiple independent long-poll workers to handle concurrent invocations. If the env var is unset or <= 1, it falls back to sequential behavior automatically — so the same handler works on both classic Lambda and Lambda Managed Instances. ([#1067](https://github.com/aws/aws-lambda-rust-runtime/pull/1067))
+
+```toml
+[dependencies]
+lambda_runtime = { version = "1.1", features = ["concurrency-tokio"] }
+```
+
+```rust
+lambda_runtime::run_concurrent(service_fn(my_handler)).await?;
+```
+
+For a complete working example, see [examples/basic-lambda-concurrent](https://github.com/aws/aws-lambda-rust-runtime/tree/main/examples/basic-lambda-concurrent). For detailed guidance on building functions for multi-concurrency, including shared state patterns and database connection pools, see the [Rust runtime for Lambda Managed Instances](https://docs.aws.amazon.com/lambda/latest/dg/lambda-managed-instances-rust.html) documentation.
 
 ### Added