Kotlin: Add Bedrock Runtime invoke model example

[amasotti]

This pull request adds a new code example demonstrating how to use the AWS SDK for Kotlin (v1.4.11) to invoke foundation models through Amazon Bedrock Runtime. The changes include:

• Add InvokeModel example showing how to generate text using Titan Text model
• Update README.md with Bedrock Runtime documentation references

The example includes:

• Set up the Bedrock Runtime client
• Structure model invocation requests
• Handle model responses using Kotlin serialization
• Process generated text output and print it to stdout

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.