Add a command that takes screenshots and writes them to a file instead of uploading

[jmuzina]

Similar issue: #1327

It would be nice if the CLI offered a new command (or perhaps a flag on percy snapshot) that saves the Percy snapshot artifacts into a local directory rather than uploading them. These artifacts could be stored serialized or as png/jpg files etc.

A potential use case for this feature is enabling public repositories to use Percy in their fork PR checks. As percy snapshot requires a Percy token secret, public repos cannot use Percy CLI to take snapshots without allowing contributors to write to their repository directly (GH actions does not expose repository secrets to forks on pull_request triggers). With this change, public repos could have a fork pull_request action take percy snapshots and archive them as a build artifact, enabling the base repo to call percy upload on those screenshot artifacts.

[ninadbstack]

We will take this as a feature request and get back to you. There is no ETA for this as of now.