fix(cx-api): adding missing readme

[IkeNefcy]

Issue

Closes #34006

Reason for this change

Readme was not added to #33983

Description of changes

Adding readme based on feature description

aws-cdk/packages/aws-cdk-lib/cx-api/README.md

Lines 698 to 714 in b577419

	* `@aws-cdk/cognito:logUserPoolClientSecretValue`
	When this feature flag is enabled, the SDK API call response to desribe user pool client values will be logged in the custom
	resource lambda function logs.
	When this feature flag is disabled, the SDK API call response to describe user pool client values will not be logged in the custom
	resource lambda function logs.
	_cdk.json_
	```json
	{
	"context": {
	"@aws-cdk/cognito:logUserPoolClientSecretValue": true
	}
	}
	```

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

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

[aws-cdk-automation]

(This review is outdated)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.98%. Comparing base (2ebc51e) to head (e48e613).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #34003   +/-   ##
=======================================
  Coverage   83.98%   83.98%           
=======================================
  Files         120      120           
  Lines        6976     6976           
  Branches     1178     1178           
=======================================
  Hits         5859     5859           
  Misses       1005     1005           
  Partials      112      112           

Flag	Coverage Δ
suite.unit	83.98% <ø> (ø)

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Components	Coverage Δ
packages/aws-cdk	∅ <ø> (∅)
packages/aws-cdk-lib/core	83.98% <ø> (ø)

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[IkeNefcy]

Exemption Request on both, just righting a wrong here

[QuantumNeuralCoder]

Exempting both. Please ensure ff documentation are included in the same PR henceforth. Thanks for this one.

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: e48e613
• Result: SUCCEEDED
• Build Logs (available for 30 days)

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