Update docs: running a custom Node.js TiddlyWiki version with npx

[vuktw]

Added the hint from this thread https://talk.tiddlywiki.org/t/tiddlywiki-docs-gettingstarted-node-js/15423 to docs

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[github-actions]

@vuktw It appears that this is your first contribution to the project, welcome.

With apologies for the bureaucracy, please could you prepare a separate PR to the 'tiddlywiki-com' branch with your signature for the Contributor License Agreement (see contributing.md).

[github-actions]

⚠️ Warning: This PR only modifies documentation (within /editions or /community/people). If the changes do not relate to the prerelease, please consider targeting the tiddlywiki-com branch instead.

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✅ Change Note Status

This PR contains documentation or configuration changes that typically don't require a change note.

[pmario]

I personally am not so happy to execute untrusted code directly from the internet. I consider a security hazard. -- I am not sure if we should promote it.

I personally vote. No

[Jermolene]

Thanks @vuktw. @pmario makes some good points but given that this is a docs change I think it would be reasonable to just add caveats in the docs that reflect the concerns that @pmario has raised.