Increase discoverability of existing bot actions via a browser extension

[JacksonKearl]

We currently have a great many bot actions, but it's not clear what they are or how to access them. A browser extension could provide a menu flyout or insert some buttons right into the issue page.

[JacksonKearl]

Current implementation (not public as I'm not sure where it will live yet). Features ability to add comments&labels, and fuzzy matches by substring similar to vscode.

I'm continuing to explore how to get the full label list to fuzzy match a la vscode.

[JacksonKearl]

Repo at: https://github.com/microsoft/vscode-github-triage-extension, with download links in the releases section.

Repo is currently private to msft, but may become public in the future.