Allow configuration files to use extension .jsonc

[brettrowberry]

VS Code allows workspace configuration via JSON files in the .vscode directory, e.g. settings.json, extensions.json, tasks.json, etc. GitHub Linguist treats them as JSON for syntax highlighting. This leads people to believe that comments aren't allowed in these files, but they are.

I propose allowing these files to use the extension .jsonc, in addition to or instead of .json.

See github-linguist/linguist#6533 for context.

[aeschli]

Duplicate of #189385

We have currently no plans for such a change. It's a good idea and I wished we would have used jsonc from the very beginning, but changing this now just adds additional complexity. In our opinion the benefits are small and do not justify the swirl.

[brettrowberry]

Thank you for your consideration.