Download manifests from a PR for editing and testing locally

[oxygen-dioxide]

Description of the new feature / enhancement

Sometimes I want to test a PR created by me or other developers on my own PC. I don't want to download the whole winget-pkgs repo. I hope that we can input the PR number and winget-create downloads the edited files in that PR into my PC.

Proposed technical implementation details

• User inputs a PR number in winget-pkgs repo
• The tool gets the added or edited manifest in the PR and save it locally

[denelon]

How is this different from: https://github.com/microsoft/winget-pkgs/blob/master/Tools/SandboxTest.ps1