doc: guide for runtime-specific conditional exports using --import

[Momena-akhtar]

Description

This PR adds a documentation guide for simulating runtime-specific conditional exports (e.g. for Electron) using --import.

It replaces the previously proposed registerCondition feature by showing a userland alternative that works without modifying Node.js core.

📄 File added: doc/contributing/runtime-conditional-exports.md

[nodejs-github-bot]

Review requested:

• @nodejs/tsc

[joyeecheung]

The document should be user-facing - doc/contributing is for Node.js core contributors, not users. Can you add the documentation to

node/doc/api/module.md

Line 1306 in 6f83e5d

### Examples

instead, following the style of other examples in the doc?

[Momena-akhtar]

Surely, yes!

The document should be user-facing - doc/contributing is for Node.js core contributors, not users. Can you add the documentation to

node/doc/api/module.md

Line 1306 in 6f83e5d

### Examples

instead, following the style of other examples in the doc?

[Momena-akhtar]

The document should be user-facing - doc/contributing is for Node.js core contributors, not users. Can you add the documentation to

node/doc/api/module.md

Line 1306 in 6f83e5d

### Examples

instead, following the style of other examples in the doc?

Thanks for the feedback on placement!

I've moved the runtime-specific conditional exports guide to the appropriate location under doc/api/esm.md, following the examples section. The new PR can be found at #59075 .

Closing this one in favor of the updated version.