chore: Add Step Function section to README

[lym953]

What does this PR do?

Adds doc for Step Functions to README, including:

1. how to instrument Step Functions in TypeScript, Python and Go
2. how to merge traces with downstream Step Functions or Lambda functions in the three languages
3. explanation of params
4. a short explanation of what the construct does
5. troubleshooting guide for one issue

Motivation

Testing Guidelines

Additional Notes

Types of Changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [x] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[lym953]

/merge

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2024-11-25 23:48:46 UTC :information_source: MergeQueue: pull request added to the queue

The median merge time in main is 8m.