Support for forked repo workflows

[vio]

• [x] check env-ci data for forked repo actions
• [x] check flow by github event (pull_request, pull_request_target)
• [x] check integrations (check, pr comment, slack) and urls

[vio]

There are multiple issues when trying to run the agent with PRs from forks:

1. pull_request event is not reporting the same data as push
2. pull_request is not exposing secrets for builds triggered from forks

To do:

• [x] fix @relative-ci/agent to report the GitHub action ref (https://github.com/relative-ci/agent/pull/284, @relative-ci/agent@1.5.1-beta.2)
• [x] fix env-ci to extract the correct data (https://github.com/pvdlg/env-ci/issues/96)
• [x] document workflow configuration based on https://securitylab.github.com/research/github-actions-preventing-pwn-requests/

[vio]

Ready for testing using relative-ci/agent-action@workflow-run-support GitHub action.

Documentation: https://relative-ci.com/documentation/setup/agent/github-action/#workflows-triggered-by-forked-repositories-beta Example: https://github.com/relative-ci/example-github-action-fork-pull-request

[vio]

Support for workflows triggered by forked repository is now available on relative-ci/agent-action@v2