Failed Storybook publishing fails "publish" action

[shawnbot]

@simurai and I ran into some funky stuff when releasing #721 tonight. you can see in this run that something very wrong happened when attempting to publish Storybook, I think inside gh-pages:

fatal: could not read Username for 'https://github.com/primer/storybook': No such device or address

Actions has an outstanding issue of duplicate runs for the same commit on the default (master) branch (I think one is for the merge commit, right @emplums?). In #707 I added automatic Storybook publishing to script/postpublish, which gets called after the npm module is successfully published. In other words, it doesn't prevent the module from being published to npm, but it does "break" the build by showing a failure in the commit statuses.

This could have just been a temporary glitch (people sometimes deploy "riskier" changes to github.com at night in the western hemisphere, when the site is less busy), but I don't think that Storybook is so important that a publishing problem should mark the publish action has having failed. So I'd like to do two things:

1. Trap errors publishing storybook so that it doesn't fail the action run.
2. Send that log over to the Actions team to see if they can give us more info (logs? not sure) about what actually failed.