Use publish tag argument in post-publish

[archmoj]

While publishing the release candidate (rc) for v2, I noticed this line should change to avoid publishing dist and locales over the tag latest.

plotly.js/tasks/sync_packages.js

Line 309 in 90ec21b

exec('npm publish', {cwd: pkgPath}, cb).stdout.pipe(process.stdout);

I made the temporary change to npm publish --tag rc at the publish time; however it would be nice to fix this before the next release.