Refs microsoft/vscode-pull-request-github#412

• macOS @misolori
• Windows @gregvanl

Complexity: 3

Authors: @RMacfarlane, @rebornix

Please test against the nightly version of the extension, which should have the most recent changes:
https://marketplace.visualstudio.com/items?itemName=GitHub.vscode-pull-request-github-insiders

When using the GitHub PR extension, a list of reviewers and labels should now be shown on the description webview for each PR. Test that

• The reviewers and labels are shown as a sidebar to the rest of the description content, but reflow to be inline below the title when the window is small
• The reviewers section lists everyone who has left already left a review or has had a review requested from them (should match github.com)
• You can request additional reviewers
• You can delete review requests from the reviewers list, but not reviewers that have already left reviews
• You can add and delete labels

Please file issues in this repo: https://github.com/Microsoft/vscode-pull-request-github

You can use https://github.com/auchenberg/pullrequest-demo for testing