Make workflow url a built-in environment variable so that it can be used in issue template

[hanabi1224]

It'd be super helpful to set the workflow url as a built-in environment variable (e.g. WORKFLOW_URL) so that one can easily add a link to the failed workflow run in the issue template.

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/store-information-in-variables#default-environment-variables

If you need to use a workflow run's URL from within a job, you can combine these variables: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID

edit: after reading the docs, I think this might belong to https://github.com/JasonEtco/actions-toolkit