Document the process.env handling and compat flags

[jasnell]

Refs: https://github.com/cloudflare/workerd/pull/3311

Summary

Screenshots (optional)

Documentation checklist

• [ ] The documentation style guide has been adhered to.
• [ ] If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• [ ] Files which have changed name or location have been allocated redirects.

[vicb]

I think the doc should mention when this flag will be active by default with nodejs_compat - 2025-04-01 it seems

[hyperlint-ai-deprecated[bot]]

Howdy and thanks for contributing to our repo. The Cloudflare team reviews new, external PRs within two (2) weeks. If it's been two weeks or longer without any movement, please tag the PR Assignees in a comment.

We review internal PRs within 1 week. If it's something urgent or has been sitting without a comment, start a thread in the Developer Docs space internally.

---

PR Change Summary

Documented the handling of process.env and compatibility flags for Node.js in the Workers documentation.

• Added a new section on populating process.env from environment variables using compatibility flags.
• Updated the environment variables documentation to clarify how Node.js compatibility flags affect variable accessibility.
• Enhanced the Node.js process documentation to explain the relationship between environment variables and process.env.

Modified Files

• src/content/docs/workers/configuration/environment-variables.mdx
• src/content/docs/workers/runtime-apis/nodejs/process.mdx

Added Files

• src/content/compatibility-flags/process-env.md

---

How can I customize these reviews?

Check out the Hyperlint AI Reviewer docs for more information on how to customize the review.

If you just want to ignore it on this PR, you can add the hyperlint-ignore label to the PR. Future changes won't trigger a Hyperlint review.

Note specifically for link checks, we only check the first 30 links in a file and we cache the results for several hours (for instance, if you just added a page, you might experience this). Our recommendation is to add hyperlint-ignore to the PR to ignore the link check for this PR.

[jasnell]

I will add disallow_importable_env in a separate PR (will add it here: https://github.com/cloudflare/cloudflare-docs/pull/24083)