Description of the feature request
Currently Secret Vars are either not available to any PR, or available to all PRs, including PRs from forked repos. Github Actions and Travis CI both allow access to secret vars from PRs from non-fork PRs.
Use case / for what or how I would use it
Making Secret Vars available to PRs from forked repos is a security risk, but making them available for internal PRs is very useful (creating signed test builds, adding comments to PRs, etc).