[CI] Don't publish NPM versions if they already exist.

[sammarks]

Just a mental note for me to remember to do this; it's cumbersome having to create new versions when debugging releases (like Flutter) simply to avoid the error we get when publishing over an existing NPM package version.

Just need to skip that publish step if the version already exists.

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[sammarks]

Brute-force solution implemented currently, where we just ignore the publish step if it fails. Obviously, not a great solution, but for the purposes of getting the website up and running, it works :)