Keyless GitHub App Tokens in Actions [Public Preview]

### Value Prop
With keyless GitHub App tokens in Actions, you can securely run workflows that act as a GitHub App without needing to store or manage private keys as secrets. This makes it easier and safer to automate tasks like creating pull requests, managing branches, or accessing private repositories, all while reducing the risk of credential leaks.

### Expected Outcome
This update aims to eliminate the need for distributing and storing private keys for GitHub Apps in Actions workflows, tightening security and simplifying setup. By allowing only trusted workflows to mint tokens based on admin-defined policies, customers gain more control and peace of mind over their automation and integrations.