Add .gitignore for common IDE/devcontainer workflow

[mjnowen]

Add a .gitignore file to exclude common development artifacts from version control:

• Dev Container configuration (.devcontainer/)
• VS Code / Cursor / Kiro IDE files (.vscode, .cursor, .kiro, *.code-workspace)
• macOS metadata files (*.DS_Store)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[ddermendzhiev]

+1

[joeysk2012]

Do we really need to put our own custom .gitignore to the main?

[mjnowen]

Hi @joeysk2012, thanks for the question — happy to expand on the rationale.

A .gitignore at the repo root is a near-universal convention across the
AWS GitHub orgs, not a custom workflow file. From a quick survey across
aws/, awslabs/, and aws-samples/, every prominent repo I checked
(aws-cli, aws-cdk, aws-sam-cli, aws-sdk-go-v2, aws-sdk-rust,
jsii, s2n-tls, serverless-application-model, mcp, llrt,
mountpoint-s3, deequ, swift-aws-lambda-runtime, aws-cdk-examples,
amazon-sagemaker-examples, …) ships one. Within amazonlinux/ itself,
amazonlinux/smart-restart already commits a .gitignore that includes
*.code-workspace, which is one of the entries proposed here.

The contents I'm proposing also aren't custom — they mirror what other
AWS-owned repos already exclude:

• *.DS_Store is excluded in essentially every AWS .gitignore I looked at
  (aws-cli, aws-cdk, aws-sdk-go-v2, aws-sdk-rust, mcp, llrt,
  aws-cdk-examples, etc.).
• .vscode / .vscode/* is excluded in aws-cdk, aws-sam-cli, s2n-tls,
  aws-sdk-go-v2, aws-sdk-rust, deequ, aidlc-workflows,
  swift-aws-lambda-runtime, nx-plugin-for-aws, and many aws-samples.
• .kiro is explicitly excluded in aws/aws-cdk, aws/aws-sam-cli,
  aws/aws-durable-execution-sdk-java, awslabs/mcp,
  awslabs/swift-aws-lambda-runtime, awslabs/nx-plugin-for-aws, and
  aws-samples/sample-collaborative-ai-dlc — it is now an established
  convention across AWS orgs.
• /.devcontainer/ and *.code-workspace appear (or close analogues
  appear) in awslabs/swift-aws-lambda-runtime, awslabs/nx-plugin-for-aws,
  aws/aws-sam-cli, and amazonlinux/smart-restart.

The closest precedent to this exact PR inside Amazon's own orgs is
awslabs/swift-aws-lambda-runtime, whose .gitignore excludes
.DS_Store, .vscode, .devcontainer, and .kiro — i.e. essentially
the same set proposed here.

The change is purely additive (no behaviour change, no build impact, just
preventing IDE/OS noise from leaking into PRs from any contributor that
uses these tools). It matches the prevailing convention in the same GitHub
organisations and helps keep future PRs clean. Happy to adjust the contents
to match the exact pattern preferred by maintainers (e.g. drop or rename any
specific entry) if that's the concern.