Github Comment Reporter: add configuration option for 'current run' link

[mjpieters]

Is your feature request related to a problem? Please describe.

I'm running Mega-Linter in Jenkins, and provide GITHUB_TOKEN, GITHUB_REPOSITORY and GITHUB_SHA environment variables so the Github Reporter knows where to post a comment. This works great.

However, the comment ends with:

See errors details in MegaLinter reports

with no further context. However, I'm also uploading the Mega-Linter reports folder as artifacts, that I'd love to link here.

Describe the solution you'd like

The reporter could take a configuration parameter (CI_ACTION_RUN_URL perhaps?) that, if set, is used as the action_run_url variable in the reporter. If set, the reporter would ignore GITHUB_RUN_ID and not generate a URL based on that, but just use the provided URL.

I can then provide the URL as built from variables set by Jenkins, such as ${BUILD_URL}/artifacts.

Describe alternatives you've considered

I would have to create a separate step that also posts a comment, as there is no option to alter the comment content before it is posted.

[nvuillam]

@mjpieters good proposition, PR is on its way :)