"Publish js library" CI job fails on PRs from forks

[makkes]

Example run from #3116.

2022-12-08T11:29:08.0843842Z ##[group]Run cd dist && npm publish
[...]
2022-12-08T11:29:08.8998941Z npm notice Publishing to https://npm.pkg.github.com
2022-12-08T11:29:09.1314429Z npm ERR! code E403
2022-12-08T11:29:09.1331815Z npm ERR! 403 403 Forbidden - PUT https://npm.pkg.github.com/@weaveworks%2fweave-gitops-main - Permission installation not allowed to Write organization package
2022-12-08T11:29:09.1333242Z npm ERR! 403 In most cases, you or one of your dependencies are requesting
2022-12-08T11:29:09.1334338Z npm ERR! 403 a package version that is forbidden by your security policy, or
2022-12-08T11:29:09.1335593Z npm ERR! 403 on a server you do not have access to.