Adds the workspace as a safe directory to circumvent fatal: detected dubious ownership in repository at '/github/workspace' type errors which were introduced into git at git/git@8959555 as a fix for https://github.blog/2022-04-12-git-security-vulnerability-announced/#cve-2022-24765 which subsequently opened up a lot of issues in github actions; actions/runner#2033 and actions/checkout#766 are examples.