Danger fails on PRs from forks

[ohitsdaniel]

Bug description

GITHUB_TOKEN does not have write permission, i.e. cannot comment on issues, in PRs triggered from forks.

Steps to reproduce

Open a pull request from a fork.
Danger fails.

Expected behavior

Danger succeeds and posts a comment.

Solution

Add a bot user with write permission on issues / PRs and expose a personal access token of said user to the PR workflows.
(See Danger docs)