Heroku: Exit code should not be zero if there is an error applying patches

When `yarn` is ran as part of a build for a Heroku application and the patches fail to apply, the exit code is `0`. I expect it to be non-zero.

This means that a Heroku application will be deployed even if the patches failed to apply (!!).

This is happening because Heroku is not detected by the [`is-ci` check](https://github.com/watson/ci-info/blob/f43f6a1cefff47fb361c88cf4b943fdbcaafe540/index.js#L52).

Related: https://github.com/ds300/patch-package/issues/143