chore: add comments to docs

[LeahMarieBush]

Description

We are migrating the terraform-cdk documentation to a unified HashiCorp product documentation repository. As a result of this migration, the unified repo (web-unified-docs) will be the source of truth.

This PR adds a notice to all existing MDX files in the original location so folks know where to contribute. We plan on deprecating and removing the files in /website.

This PR will be merged after docs have been migrated

Checklist

• I have updated the PR title to match CDKTF's style guide
• I have run the linter on my code locally
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation if applicable
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works if applicable
• New and existing unit tests pass locally with my changes

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[LeahMarieBush]

Hello! I'm not familiar with the tests that run on these PRs but I don't think my changes would cause integration test failures. Can someone who is more familiar with this repo help me debug this to unblock this PR?