cross-ci/lib/var/JOB_URL.d.ts

`cross-ci` standardizes environment variables for CI. For example, your can simply use `BUILD_BRANCH` variable in all CI runners instead of `CIRCLE_BRANCH` in CircleCI or `TRAVIS_PULL_REQUEST_BRANCH` in Travis.

declare const JOB_URL: () => string;
export = JOB_URL;