Add Web Client support for the VSCode extension

[kristoff-it]

The VSCode extension is pretty much already all set for working in a web client, like vscode.dev, but for some reason it doesn't work.

I added the browser entry point in packages.json like the docs suggest, but it still doesn't work. I also tried to get local testing going but couldn't get that to work either (delicious out of date docs, thanks Microsoft) so I'm leaving the fun of getting this stuff to work to a willing contributor (who would benefit from this, ideally).

At the application level, nothing in the extension really needs APIs that are not available in the browser, I think, but I'm sure that there's a bunch of small adjustments required to make this true in a concrete sense.

The vscode extension source lives under editors/vscode.